Merge pull request #11 from JF002/date-library

Date/Time management

13 files changed, 23451 insertions, 24 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 43ef24f1..7fbb2ebe 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -64,10 +64,19 @@ set(INCLUDE_FILES
   drivers/Cst816s.h
   FreeRTOS/portmacro.h
   FreeRTOS/portmacro_cmsis.h
+  libs/date/includes/date/tz.h
+  libs/date/includes/date/chrono_io.h
+  libs/date/includes/date/date.h
+  libs/date/includes/date/islamic.h
+  libs/date/includes/date/iso_week.h
+  libs/date/includes/date/julian.h
+  libs/date/includes/date/ptz.h
+  libs/date/includes/date/tz_private.h
 )
 
 include_directories(
   FreeRTOS/
+  libs/date/includes
 )
 
 nRF5x_addExecutable(pinetime-app "${SOURCE_FILES}")
\ No newline at end of file
diff --git a/src/DisplayApp/DisplayApp.cpp b/src/DisplayApp/DisplayApp.cpp
index 2a26f189..99c606d3 100644
--- a/src/DisplayApp/DisplayApp.cpp
+++ b/src/DisplayApp/DisplayApp.cpp
@@ -9,6 +9,9 @@
 #include <queue.h>
 #include <Components/DateTime/DateTimeController.h>
 #include <drivers/Cst816s.h>
+#include <chrono>
+#include <string>
+#include <date/date.h>
 
 using namespace Pinetime::Applications;
 
@@ -102,6 +105,11 @@ void DisplayApp::InitHw() {
   gfx->DrawString(10, 0, 0x0000, "BLE", &smallFont, false);
   gfx->DrawString(20, 180, 0xffff, "", &smallFont, false);
 
+  currentChar[0] = 0;
+  currentChar[1] = 0;
+  currentChar[2] = 0;
+  currentChar[3] = 0;
+
   touchPanel.Init();
 }
 
@@ -138,11 +146,6 @@ void DisplayApp::Refresh() {
         state = States::Running;
         break;
       case Messages::UpdateDateTime:
-        deltaSeconds = nrf_rtc_counter_get(portNRF_RTC_REG) / 1000;
-        this->seconds = dateTimeController.Seconds();
-        this->minutes = dateTimeController.Minutes();
-        this->hours = dateTimeController.Hours();
-        dateUpdated = true;
         break;
       case Messages::UpdateBleConnection:
         bleConnectionUpdated = true;
@@ -181,18 +184,35 @@ void DisplayApp::RunningState() {
   auto raw = systick_counter / 1000;
   auto currentDeltaSeconds = raw - deltaSeconds;
 
-  auto deltaMinutes = (currentDeltaSeconds / 60);
-  auto currentMinutes = minutes + deltaMinutes;
+  std::chrono::time_point<std::chrono::system_clock, std::chrono::milliseconds> currentDateTime;
+  currentDateTime += date::years( dateTimeController.Year()-1970);
+  currentDateTime += date::days( dateTimeController.Day() - 1);
+  currentDateTime += date::months( (int)dateTimeController.Month() - 1);
+
+  currentDateTime += std::chrono::hours(dateTimeController.Hours());
+  currentDateTime += std::chrono::minutes (dateTimeController.Minutes());
+  currentDateTime += std::chrono::seconds(dateTimeController.Seconds() + currentDeltaSeconds);
+
+  currentDateTime -= std::chrono::hours(3); // TODO WHYYYY?
+
+  auto dp = date::floor<date::days>(currentDateTime);
+  auto time = date::make_time(currentDateTime-dp);
+  auto ymd = date::year_month_day(dp);
 
-  auto deltaHours = currentMinutes / 60;
-  currentMinutes -= (deltaHours * 60);
-  auto currentHours = hours + deltaHours;
+  auto year = (int)ymd.year();
+  auto month = (unsigned)ymd.month();
+  auto day = (unsigned)ymd.day();
+  auto weekday = date::weekday(ymd);
+
+  auto hh = time.hours().count();
+  auto mm = time.minutes().count();
+  auto ss = time.seconds().count();
 
   char minutesChar[3];
-  sprintf(minutesChar, "%02d", currentMinutes);
+  sprintf(minutesChar, "%02d", mm);
 
   char hoursChar[3];
-  sprintf(hoursChar, "%02d", currentHours);
+  sprintf(hoursChar, "%02d", hh);
 
   uint8_t x = 7;
   if (hoursChar[0] != currentChar[0]) {
@@ -218,16 +238,13 @@ void DisplayApp::RunningState() {
     currentChar[3] = minutesChar[1];
   }
 
-  if (dateUpdated) {
-    auto year = dateTimeController.Year();
-    auto month = dateTimeController.Month();
-    auto day = dateTimeController.Day();
-    auto dayOfWeek = dateTimeController.DayOfWeek();
-
+  if (ymd != currentYmd) {
+    gfx->FillRectangle(0,180, 240, 15, 0x0000);
     char dateStr[22];
-    sprintf(dateStr, "%s %d %s %d", DayOfWeekToString(dayOfWeek), day, MonthToString(month), year);
+    sprintf(dateStr, "%s %d %s %d", DayOfWeekToString(Pinetime::Controllers::DateTime::Days(weekday.iso_encoding())), day, MonthToString((Pinetime::Controllers::DateTime::Months )month), year);
     gfx->DrawString(10, 180, 0xffff, dateStr, &smallFont, false);
-    dateUpdated = false;
+
+    currentYmd = ymd;
   }
 }
 
diff --git a/src/DisplayApp/DisplayApp.h b/src/DisplayApp/DisplayApp.h
index 75c74227..1e9e2e89 100644
--- a/src/DisplayApp/DisplayApp.h
+++ b/src/DisplayApp/DisplayApp.h
@@ -11,6 +11,7 @@
 #include <Components/DateTime/DateTimeController.h>
 #include "lcdfont14.h"
 #include "../drivers/Cst816s.h"
+#include <date/date.h>
 
 
 extern const FONT_INFO lCD_70ptFontInfo;
@@ -40,11 +41,10 @@ namespace Pinetime {
 
         static const char* MonthToString(Pinetime::Controllers::DateTime::Months month);
         static const char* DayOfWeekToString(Pinetime::Controllers::DateTime::Days dayOfWeek);
-        uint8_t seconds = 0;
-        uint8_t minutes = 0;
-        uint8_t hours = 0;
+
         char currentChar[4];
         uint32_t deltaSeconds = 0;
+        date::year_month_day currentYmd;
 
         States state = States::Running;
         void RunningState();
@@ -62,7 +62,6 @@ namespace Pinetime {
 
         static char const *DaysString[];
         static char const *MonthsString[];
-        bool dateUpdated = false;
 
         Pinetime::Drivers::Cst816S touchPanel;
         void OnTouchEvent();
diff --git a/src/libs/date/includes/date/chrono_io.h b/src/libs/date/includes/date/chrono_io.h
new file mode 100644
index 00000000..21be4040
--- /dev/null
+++ b/src/libs/date/includes/date/chrono_io.h
@@ -0,0 +1,34 @@
+#ifndef CHRONO_IO_H
+#define CHRONO_IO_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2016, 2017 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+// This functionality has moved to "date.h"
+
+#include "date.h"
+
+#endif  // CHRONO_IO_H
diff --git a/src/libs/date/includes/date/date.h b/src/libs/date/includes/date/date.h
new file mode 100644
index 00000000..027a5a46
--- /dev/null
+++ b/src/libs/date/includes/date/date.h
@@ -0,0 +1,7947 @@
+#ifndef DATE_H
+#define DATE_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2015, 2016, 2017 Howard Hinnant
+// Copyright (c) 2016 Adrian Colomitchi
+// Copyright (c) 2017 Florian Dang
+// Copyright (c) 2017 Paul Thompson
+// Copyright (c) 2018, 2019 Tomasz Kamiński
+// Copyright (c) 2019 Jiangang Zhuang
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+#ifndef HAS_STRING_VIEW
+#  if __cplusplus >= 201703 || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
+#    define HAS_STRING_VIEW 1
+#  else
+#    define HAS_STRING_VIEW 0
+#  endif
+#endif  // HAS_STRING_VIEW
+
+#include <cassert>
+#include <algorithm>
+#include <cctype>
+#include <chrono>
+#include <climits>
+#if !(__cplusplus >= 201402)
+#  include <cmath>
+#endif
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <ctime>
+#include <ios>
+#include <istream>
+#include <iterator>
+#include <limits>
+#include <locale>
+#include <memory>
+#include <ostream>
+#include <ratio>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#if HAS_STRING_VIEW
+# include <string_view>
+#endif
+#include <utility>
+#include <type_traits>
+
+#ifdef __GNUC__
+# pragma GCC diagnostic push
+# if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR > 7)
+#  pragma GCC diagnostic ignored "-Wpedantic"
+# endif
+# if __GNUC__ < 5
+   // GCC 4.9 Bug 61489 Wrong warning with -Wmissing-field-initializers
+#  pragma GCC diagnostic ignored "-Wmissing-field-initializers"
+# endif
+#endif
+
+#ifdef _MSC_VER
+#   pragma warning(push)
+// warning C4127: conditional expression is constant
+#   pragma warning(disable : 4127)
+#endif
+
+namespace date
+{
+
+//---------------+
+// Configuration |
+//---------------+
+
+#ifndef ONLY_C_LOCALE
+#  define ONLY_C_LOCALE 0
+#endif
+
+#if defined(_MSC_VER) && (!defined(__clang__) || (_MSC_VER < 1910))
+// MSVC
+#  ifndef _SILENCE_CXX17_UNCAUGHT_EXCEPTION_DEPRECATION_WARNING
+#    define _SILENCE_CXX17_UNCAUGHT_EXCEPTION_DEPRECATION_WARNING
+#  endif
+#  if _MSC_VER < 1910
+//   before VS2017
+#    define CONSTDATA const
+#    define CONSTCD11
+#    define CONSTCD14
+#    define NOEXCEPT _NOEXCEPT
+#  else
+//   VS2017 and later
+#    define CONSTDATA constexpr const
+#    define CONSTCD11 constexpr
+#    define CONSTCD14 constexpr
+#    define NOEXCEPT noexcept
+#  endif
+
+#elif defined(__SUNPRO_CC) && __SUNPRO_CC <= 0x5150
+// Oracle Developer Studio 12.6 and earlier
+#  define CONSTDATA constexpr const
+#  define CONSTCD11 constexpr
+#  define CONSTCD14
+#  define NOEXCEPT noexcept
+
+#elif __cplusplus >= 201402
+// C++14
+#  define CONSTDATA constexpr const
+#  define CONSTCD11 constexpr
+#  define CONSTCD14 constexpr
+#  define NOEXCEPT noexcept
+#else
+// C++11
+#  define CONSTDATA constexpr const
+#  define CONSTCD11 constexpr
+#  define CONSTCD14
+#  define NOEXCEPT noexcept
+#endif
+
+#ifndef HAS_UNCAUGHT_EXCEPTIONS
+#  if __cplusplus > 201703 || (defined(_MSVC_LANG) && _MSVC_LANG > 201703L)
+#    define HAS_UNCAUGHT_EXCEPTIONS 1
+#  else
+#    define HAS_UNCAUGHT_EXCEPTIONS 0
+#  endif
+#endif  // HAS_UNCAUGHT_EXCEPTIONS
+
+#ifndef HAS_VOID_T
+#  if __cplusplus >= 201703 || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
+#    define HAS_VOID_T 1
+#  else
+#    define HAS_VOID_T 0
+#  endif
+#endif  // HAS_VOID_T
+
+// Protect from Oracle sun macro
+#ifdef sun
+#  undef sun
+#endif
+
+// Work around for a NVCC compiler bug which causes it to fail
+// to compile std::ratio_{multiply,divide} when used directly
+// in the std::chrono::duration template instantiations below
+namespace detail {
+template <typename R1, typename R2>
+using ratio_multiply = decltype(std::ratio_multiply<R1, R2>{});
+
+template <typename R1, typename R2>
+using ratio_divide = decltype(std::ratio_divide<R1, R2>{});
+}  // namespace detail
+
+//-----------+
+// Interface |
+//-----------+
+
+// durations
+
+using days = std::chrono::duration
+    <int, detail::ratio_multiply<std::ratio<24>, std::chrono::hours::period>>;
+
+using weeks = std::chrono::duration
+    <int, detail::ratio_multiply<std::ratio<7>, days::period>>;
+
+using years = std::chrono::duration
+    <int, detail::ratio_multiply<std::ratio<146097, 400>, days::period>>;
+
+using months = std::chrono::duration
+    <int, detail::ratio_divide<years::period, std::ratio<12>>>;
+
+// time_point
+
+template <class Duration>
+    using sys_time = std::chrono::time_point<std::chrono::system_clock, Duration>;
+
+using sys_days    = sys_time<days>;
+using sys_seconds = sys_time<std::chrono::seconds>;
+
+struct local_t {};
+
+template <class Duration>
+    using local_time = std::chrono::time_point<local_t, Duration>;
+
+using local_seconds = local_time<std::chrono::seconds>;
+using local_days    = local_time<days>;
+
+// types
+
+struct last_spec
+{
+    explicit last_spec() = default;
+};
+
+class day;
+class month;
+class year;
+
+class weekday;
+class weekday_indexed;
+class weekday_last;
+
+class month_day;
+class month_day_last;
+class month_weekday;
+class month_weekday_last;
+
+class year_month;
+
+class year_month_day;
+class year_month_day_last;
+class year_month_weekday;
+class year_month_weekday_last;
+
+// date composition operators
+
+CONSTCD11 year_month operator/(const year& y, const month& m) NOEXCEPT;
+CONSTCD11 year_month operator/(const year& y, int          m) NOEXCEPT;
+
+CONSTCD11 month_day operator/(const day& d, const month& m) NOEXCEPT;
+CONSTCD11 month_day operator/(const day& d, int          m) NOEXCEPT;
+CONSTCD11 month_day operator/(const month& m, const day& d) NOEXCEPT;
+CONSTCD11 month_day operator/(const month& m, int        d) NOEXCEPT;
+CONSTCD11 month_day operator/(int          m, const day& d) NOEXCEPT;
+
+CONSTCD11 month_day_last operator/(const month& m, last_spec) NOEXCEPT;
+CONSTCD11 month_day_last operator/(int          m, last_spec) NOEXCEPT;
+CONSTCD11 month_day_last operator/(last_spec, const month& m) NOEXCEPT;
+CONSTCD11 month_day_last operator/(last_spec, int          m) NOEXCEPT;
+
+CONSTCD11 month_weekday operator/(const month& m, const weekday_indexed& wdi) NOEXCEPT;
+CONSTCD11 month_weekday operator/(int          m, const weekday_indexed& wdi) NOEXCEPT;
+CONSTCD11 month_weekday operator/(const weekday_indexed& wdi, const month& m) NOEXCEPT;
+CONSTCD11 month_weekday operator/(const weekday_indexed& wdi, int          m) NOEXCEPT;
+
+CONSTCD11 month_weekday_last operator/(const month& m, const weekday_last& wdl) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(int          m, const weekday_last& wdl) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(const weekday_last& wdl, const month& m) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(const weekday_last& wdl, int          m) NOEXCEPT;
+
+CONSTCD11 year_month_day operator/(const year_month& ym, const day& d) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const year_month& ym, int        d) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const year& y, const month_day& md) NOEXCEPT;
+CONSTCD11 year_month_day operator/(int         y, const month_day& md) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const month_day& md, const year& y) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const month_day& md, int         y) NOEXCEPT;
+
+CONSTCD11
+    year_month_day_last operator/(const year_month& ym,   last_spec) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const year& y, const month_day_last& mdl) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(int         y, const month_day_last& mdl) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const month_day_last& mdl, const year& y) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const month_day_last& mdl, int         y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const year_month& ym, const weekday_indexed& wdi) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const year&        y, const month_weekday&   mwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(int                y, const month_weekday&   mwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const month_weekday& mwd, const year&          y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const month_weekday& mwd, int                  y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const year_month& ym, const weekday_last& wdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const year& y, const month_weekday_last& mwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(int         y, const month_weekday_last& mwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, const year& y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, int         y) NOEXCEPT;
+
+// Detailed interface
+
+// day
+
+class day
+{
+    unsigned char d_;
+
+public:
+    day() = default;
+    explicit CONSTCD11 day(unsigned d) NOEXCEPT;
+
+    CONSTCD14 day& operator++()    NOEXCEPT;
+    CONSTCD14 day  operator++(int) NOEXCEPT;
+    CONSTCD14 day& operator--()    NOEXCEPT;
+    CONSTCD14 day  operator--(int) NOEXCEPT;
+
+    CONSTCD14 day& operator+=(const days& d) NOEXCEPT;
+    CONSTCD14 day& operator-=(const days& d) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const day& x, const day& y) NOEXCEPT;
+
+CONSTCD11 day  operator+(const day&  x, const days& y) NOEXCEPT;
+CONSTCD11 day  operator+(const days& x, const day&  y) NOEXCEPT;
+CONSTCD11 day  operator-(const day&  x, const days& y) NOEXCEPT;
+CONSTCD11 days operator-(const day&  x, const day&  y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const day& d);
+
+// month
+
+class month
+{
+    unsigned char m_;
+
+public:
+    month() = default;
+    explicit CONSTCD11 month(unsigned m) NOEXCEPT;
+
+    CONSTCD14 month& operator++()    NOEXCEPT;
+    CONSTCD14 month  operator++(int) NOEXCEPT;
+    CONSTCD14 month& operator--()    NOEXCEPT;
+    CONSTCD14 month  operator--(int) NOEXCEPT;
+
+    CONSTCD14 month& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 month& operator-=(const months& m) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month& x, const month& y) NOEXCEPT;
+
+CONSTCD14 month  operator+(const month&  x, const months& y) NOEXCEPT;
+CONSTCD14 month  operator+(const months& x,  const month& y) NOEXCEPT;
+CONSTCD14 month  operator-(const month&  x, const months& y) NOEXCEPT;
+CONSTCD14 months operator-(const month&  x,  const month& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month& m);
+
+// year
+
+class year
+{
+    short y_;
+
+public:
+    year() = default;
+    explicit CONSTCD11 year(int y) NOEXCEPT;
+
+    CONSTCD14 year& operator++()    NOEXCEPT;
+    CONSTCD14 year  operator++(int) NOEXCEPT;
+    CONSTCD14 year& operator--()    NOEXCEPT;
+    CONSTCD14 year  operator--(int) NOEXCEPT;
+
+    CONSTCD14 year& operator+=(const years& y) NOEXCEPT;
+    CONSTCD14 year& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 year operator-() const NOEXCEPT;
+    CONSTCD11 year operator+() const NOEXCEPT;
+
+    CONSTCD11 bool is_leap() const NOEXCEPT;
+
+    CONSTCD11 explicit operator int() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+    static CONSTCD11 year min() NOEXCEPT { return year{-32767}; }
+    static CONSTCD11 year max() NOEXCEPT { return year{32767}; }
+};
+
+CONSTCD11 bool operator==(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year& x, const year& y) NOEXCEPT;
+
+CONSTCD11 year  operator+(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 year  operator+(const years& x, const year&  y) NOEXCEPT;
+CONSTCD11 year  operator-(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 years operator-(const year&  x, const year&  y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y);
+
+// weekday
+
+class weekday
+{
+    unsigned char wd_;
+public:
+    weekday() = default;
+    explicit CONSTCD11 weekday(unsigned wd) NOEXCEPT;
+    CONSTCD14 weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD14 explicit weekday(const local_days& dp) NOEXCEPT;
+
+    CONSTCD14 weekday& operator++()    NOEXCEPT;
+    CONSTCD14 weekday  operator++(int) NOEXCEPT;
+    CONSTCD14 weekday& operator--()    NOEXCEPT;
+    CONSTCD14 weekday  operator--(int) NOEXCEPT;
+
+    CONSTCD14 weekday& operator+=(const days& d) NOEXCEPT;
+    CONSTCD14 weekday& operator-=(const days& d) NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+    CONSTCD11 unsigned c_encoding() const NOEXCEPT;
+    CONSTCD11 unsigned iso_encoding() const NOEXCEPT;
+
+    CONSTCD11 weekday_indexed operator[](unsigned index) const NOEXCEPT;
+    CONSTCD11 weekday_last    operator[](last_spec)      const NOEXCEPT;
+
+private:
+    static CONSTCD14 unsigned char weekday_from_days(int z) NOEXCEPT;
+
+    friend CONSTCD11 bool operator==(const weekday& x, const weekday& y) NOEXCEPT;
+    friend CONSTCD14 days operator-(const weekday& x, const weekday& y) NOEXCEPT;
+    friend CONSTCD14 weekday operator+(const weekday& x, const days& y) NOEXCEPT;
+    template<class CharT, class Traits>
+        friend std::basic_ostream<CharT, Traits>&
+            operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd);
+    friend class weekday_indexed;
+};
+
+CONSTCD11 bool operator==(const weekday& x, const weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday& x, const weekday& y) NOEXCEPT;
+
+CONSTCD14 weekday operator+(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 weekday operator+(const days&    x, const weekday& y) NOEXCEPT;
+CONSTCD14 weekday operator-(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 days    operator-(const weekday& x, const weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd);
+
+// weekday_indexed
+
+class weekday_indexed
+{
+    unsigned char wd_    : 4;
+    unsigned char index_ : 4;
+
+public:
+    weekday_indexed() = default;
+    CONSTCD11 weekday_indexed(const date::weekday& wd, unsigned index) NOEXCEPT;
+
+    CONSTCD11 date::weekday weekday() const NOEXCEPT;
+    CONSTCD11 unsigned index() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_indexed& wdi);
+
+// weekday_last
+
+class weekday_last
+{
+    date::weekday wd_;
+
+public:
+    explicit CONSTCD11 weekday_last(const date::weekday& wd) NOEXCEPT;
+
+    CONSTCD11 date::weekday weekday() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday_last& x, const weekday_last& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday_last& x, const weekday_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_last& wdl);
+
+namespace detail
+{
+
+struct unspecified_month_disambiguator {};
+
+}  // namespace detail
+
+// year_month
+
+class year_month
+{
+    date::year  y_;
+    date::month m_;
+
+public:
+    year_month() = default;
+    CONSTCD11 year_month(const date::year& y, const date::month& m) NOEXCEPT;
+
+    CONSTCD11 date::year  year()  const NOEXCEPT;
+    CONSTCD11 date::month month() const NOEXCEPT;
+
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month& operator+=(const months& dm) NOEXCEPT;
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month& operator-=(const months& dm) NOEXCEPT;
+    CONSTCD14 year_month& operator+=(const years& dy) NOEXCEPT;
+    CONSTCD14 year_month& operator-=(const years& dy) NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_month& x, const year_month& y) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14 year_month operator+(const year_month& ym, const months& dm) NOEXCEPT;
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14 year_month operator+(const months& dm, const year_month& ym) NOEXCEPT;
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14 year_month operator-(const year_month& ym, const months& dm) NOEXCEPT;
+
+CONSTCD11 months operator-(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 year_month operator+(const year_month& ym, const years& dy) NOEXCEPT;
+CONSTCD11 year_month operator+(const years& dy, const year_month& ym) NOEXCEPT;
+CONSTCD11 year_month operator-(const year_month& ym, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month& ym);
+
+// month_day
+
+class month_day
+{
+    date::month m_;
+    date::day   d_;
+
+public:
+    month_day() = default;
+    CONSTCD11 month_day(const date::month& m, const date::day& d) NOEXCEPT;
+
+    CONSTCD11 date::month month() const NOEXCEPT;
+    CONSTCD11 date::day   day() const NOEXCEPT;
+
+    CONSTCD14 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month_day& x, const month_day& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day& md);
+
+// month_day_last
+
+class month_day_last
+{
+    date::month m_;
+
+public:
+    CONSTCD11 explicit month_day_last(const date::month& m) NOEXCEPT;
+
+    CONSTCD11 date::month month() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day_last& mdl);
+
+// month_weekday
+
+class month_weekday
+{
+    date::month           m_;
+    date::weekday_indexed wdi_;
+public:
+    CONSTCD11 month_weekday(const date::month& m,
+                            const date::weekday_indexed& wdi) NOEXCEPT;
+
+    CONSTCD11 date::month           month()           const NOEXCEPT;
+    CONSTCD11 date::weekday_indexed weekday_indexed() const NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_weekday& x, const month_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_weekday& x, const month_weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday& mwd);
+
+// month_weekday_last
+
+class month_weekday_last
+{
+    date::month        m_;
+    date::weekday_last wdl_;
+
+public:
+    CONSTCD11 month_weekday_last(const date::month& m,
+                                 const date::weekday_last& wd) NOEXCEPT;
+
+    CONSTCD11 date::month        month()        const NOEXCEPT;
+    CONSTCD11 date::weekday_last weekday_last() const NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday_last& mwdl);
+
+// class year_month_day
+
+class year_month_day
+{
+    date::year  y_;
+    date::month m_;
+    date::day   d_;
+
+public:
+    year_month_day() = default;
+    CONSTCD11 year_month_day(const date::year& y, const date::month& m,
+                             const date::day& d) NOEXCEPT;
+    CONSTCD14 year_month_day(const year_month_day_last& ymdl) NOEXCEPT;
+
+    CONSTCD14 year_month_day(sys_days dp) NOEXCEPT;
+    CONSTCD14 explicit year_month_day(local_days dp) NOEXCEPT;
+
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_day& operator+=(const months& m) NOEXCEPT;
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_day& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_day& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 date::year  year()  const NOEXCEPT;
+    CONSTCD11 date::month month() const NOEXCEPT;
+    CONSTCD11 date::day   day()   const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD14 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD14 year_month_day from_days(days dp) NOEXCEPT;
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14 year_month_day operator+(const year_month_day& ymd, const months& dm) NOEXCEPT;
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14 year_month_day operator+(const months& dm, const year_month_day& ymd) NOEXCEPT;
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14 year_month_day operator-(const year_month_day& ymd, const months& dm) NOEXCEPT;
+CONSTCD11 year_month_day operator+(const year_month_day& ymd, const years& dy)  NOEXCEPT;
+CONSTCD11 year_month_day operator+(const years& dy, const year_month_day& ymd)  NOEXCEPT;
+CONSTCD11 year_month_day operator-(const year_month_day& ymd, const years& dy)  NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day& ymd);
+
+// year_month_day_last
+
+class year_month_day_last
+{
+    date::year           y_;
+    date::month_day_last mdl_;
+
+public:
+    CONSTCD11 year_month_day_last(const date::year& y,
+                                  const date::month_day_last& mdl) NOEXCEPT;
+
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_day_last& operator+=(const months& m) NOEXCEPT;
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_day_last& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 date::year           year()           const NOEXCEPT;
+    CONSTCD11 date::month          month()          const NOEXCEPT;
+    CONSTCD11 date::month_day_last month_day_last() const NOEXCEPT;
+    CONSTCD14 date::day            day()            const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator< (const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator> (const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator<=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator>=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const months& dm) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_day_last
+operator+(const months& dm, const year_month_day_last& ymdl) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator+(const years& dy, const year_month_day_last& ymdl) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day_last& ymdl);
+
+// year_month_weekday
+
+class year_month_weekday
+{
+    date::year            y_;
+    date::month           m_;
+    date::weekday_indexed wdi_;
+
+public:
+    year_month_weekday() = default;
+    CONSTCD11 year_month_weekday(const date::year& y, const date::month& m,
+                                   const date::weekday_indexed& wdi) NOEXCEPT;
+    CONSTCD14 year_month_weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD14 explicit year_month_weekday(const local_days& dp) NOEXCEPT;
+
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_weekday& operator+=(const months& m) NOEXCEPT;
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_weekday& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 date::year year() const NOEXCEPT;
+    CONSTCD11 date::month month() const NOEXCEPT;
+    CONSTCD11 date::weekday weekday() const NOEXCEPT;
+    CONSTCD11 unsigned index() const NOEXCEPT;
+    CONSTCD11 date::weekday_indexed weekday_indexed() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD14 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD14 year_month_weekday from_days(days dp) NOEXCEPT;
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const months& dm) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_weekday
+operator+(const months& dm, const year_month_weekday& ymwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator+(const years& dy, const year_month_weekday& ymwd) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday& ymwdi);
+
+// year_month_weekday_last
+
+class year_month_weekday_last
+{
+    date::year y_;
+    date::month m_;
+    date::weekday_last wdl_;
+
+public:
+    CONSTCD11 year_month_weekday_last(const date::year& y, const date::month& m,
+                                      const date::weekday_last& wdl) NOEXCEPT;
+
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_weekday_last& operator+=(const months& m) NOEXCEPT;
+    template<class = detail::unspecified_month_disambiguator>
+    CONSTCD14 year_month_weekday_last& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator+=(const years& y) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 date::year year() const NOEXCEPT;
+    CONSTCD11 date::month month() const NOEXCEPT;
+    CONSTCD11 date::weekday weekday() const NOEXCEPT;
+    CONSTCD11 date::weekday_last weekday_last() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+private:
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11
+bool
+operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT;
+
+CONSTCD11
+bool
+operator!=(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_weekday_last
+operator+(const months& dm, const year_month_weekday_last& ymwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator+(const years& dy, const year_month_weekday_last& ymwdl) NOEXCEPT;
+
+template<class = detail::unspecified_month_disambiguator>
+CONSTCD14
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday_last& ymwdl);
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+inline namespace literals
+{
+
+CONSTCD11 date::day  operator "" _d(unsigned long long d) NOEXCEPT;
+CONSTCD11 date::year operator "" _y(unsigned long long y) NOEXCEPT;
+
+}  // inline namespace literals
+#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+// CONSTDATA date::month January{1};
+// CONSTDATA date::month February{2};
+// CONSTDATA date::month March{3};
+// CONSTDATA date::month April{4};
+// CONSTDATA date::month May{5};
+// CONSTDATA date::month June{6};
+// CONSTDATA date::month July{7};
+// CONSTDATA date::month August{8};
+// CONSTDATA date::month September{9};
+// CONSTDATA date::month October{10};
+// CONSTDATA date::month November{11};
+// CONSTDATA date::month December{12};
+//
+// CONSTDATA date::weekday Sunday{0u};
+// CONSTDATA date::weekday Monday{1u};
+// CONSTDATA date::weekday Tuesday{2u};
+// CONSTDATA date::weekday Wednesday{3u};
+// CONSTDATA date::weekday Thursday{4u};
+// CONSTDATA date::weekday Friday{5u};
+// CONSTDATA date::weekday Saturday{6u};
+
+#if HAS_VOID_T
+
+template <class T, class = std::void_t<>>
+struct is_clock
+    : std::false_type
+{};
+
+template <class T>
+struct is_clock<T, std::void_t<decltype(T::now()), typename T::rep, typename T::period,
+                               typename T::duration, typename T::time_point,
+                               decltype(T::is_steady)>>
+    : std::true_type
+{};
+
+#endif  // HAS_VOID_T
+
+//----------------+
+// Implementation |
+//----------------+
+
+// utilities
+namespace detail {
+
+template<class CharT, class Traits = std::char_traits<CharT>>
+class save_istream
+{
+protected:
+    std::basic_ios<CharT, Traits>& is_;
+    CharT fill_;
+    std::ios::fmtflags flags_;
+    std::streamsize width_;
+    std::basic_ostream<CharT, Traits>* tie_;
+    std::locale loc_;
+
+public:
+    ~save_istream()
+    {
+        is_.fill(fill_);
+        is_.flags(flags_);
+        is_.width(width_);
+        is_.imbue(loc_);
+        is_.tie(tie_);
+    }
+
+    save_istream(const save_istream&) = delete;
+    save_istream& operator=(const save_istream&) = delete;
+
+    explicit save_istream(std::basic_ios<CharT, Traits>& is)
+        : is_(is)
+        , fill_(is.fill())
+        , flags_(is.flags())
+        , width_(is.width(0))
+        , tie_(is.tie(nullptr))
+        , loc_(is.getloc())
+        {
+            if (tie_ != nullptr)
+                tie_->flush();
+        }
+};
+
+template<class CharT, class Traits = std::char_traits<CharT>>
+class save_ostream
+    : private save_istream<CharT, Traits>
+{
+public:
+    ~save_ostream()
+    {
+        if ((this->flags_ & std::ios::unitbuf) &&
+#if HAS_UNCAUGHT_EXCEPTIONS
+                std::uncaught_exceptions() == 0 &&
+#else
+                !std::uncaught_exception() &&
+#endif
+                this->is_.good())
+            this->is_.rdbuf()->pubsync();
+    }
+
+    save_ostream(const save_ostream&) = delete;
+    save_ostream& operator=(const save_ostream&) = delete;
+
+    explicit save_ostream(std::basic_ios<CharT, Traits>& os)
+        : save_istream<CharT, Traits>(os)
+        {
+        }
+};
+
+template <class T>
+struct choose_trunc_type
+{
+    static const int digits = std::numeric_limits<T>::digits;
+    using type = typename std::conditional
+                 <
+                     digits < 32,
+                     std::int32_t,
+                     typename std::conditional
+                     <
+                         digits < 64,
+                         std::int64_t,
+#ifdef __SIZEOF_INT128__
+                         __int128
+#else
+                         std::int64_t
+#endif
+                     >::type
+                 >::type;
+};
+
+template <class T>
+CONSTCD11
+inline
+typename std::enable_if
+<
+    !std::chrono::treat_as_floating_point<T>::value,
+    T
+>::type
+trunc(T t) NOEXCEPT
+{
+    return t;
+}
+
+template <class T>
+CONSTCD14
+inline
+typename std::enable_if
+<
+    std::chrono::treat_as_floating_point<T>::value,
+    T
+>::type
+trunc(T t) NOEXCEPT
+{
+    using std::numeric_limits;
+    using I = typename choose_trunc_type<T>::type;
+    CONSTDATA auto digits = numeric_limits<T>::digits;
+    static_assert(digits < numeric_limits<I>::digits, "");
+    CONSTDATA auto max = I{1} << (digits-1);
+    CONSTDATA auto min = -max;
+    const auto negative = t < T{0};
+    if (min <= t && t <= max && t != 0 && t == t)
+    {
+        t = static_cast<T>(static_cast<I>(t));
+        if (t == 0 && negative)
+            t = -t;
+    }
+    return t;
+}
+
+template <std::intmax_t Xp, std::intmax_t Yp>
+struct static_gcd
+{
+    static const std::intmax_t value = static_gcd<Yp, Xp % Yp>::value;
+};
+
+template <std::intmax_t Xp>
+struct static_gcd<Xp, 0>
+{
+    static const std::intmax_t value = Xp;
+};
+
+template <>
+struct static_gcd<0, 0>
+{
+    static const std::intmax_t value = 1;
+};
+
+template <class R1, class R2>
+struct no_overflow
+{
+private:
+    static const std::intmax_t gcd_n1_n2 = static_gcd<R1::num, R2::num>::value;
+    static const std::intmax_t gcd_d1_d2 = static_gcd<R1::den, R2::den>::value;
+    static const std::intmax_t n1 = R1::num / gcd_n1_n2;
+    static const std::intmax_t d1 = R1::den / gcd_d1_d2;
+    static const std::intmax_t n2 = R2::num / gcd_n1_n2;
+    static const std::intmax_t d2 = R2::den / gcd_d1_d2;
+    static const std::intmax_t max = std::numeric_limits<std::intmax_t>::max();
+
+    template <std::intmax_t Xp, std::intmax_t Yp, bool overflow>
+    struct mul    // overflow == false
+    {
+        static const std::intmax_t value = Xp * Yp;
+    };
+
+    template <std::intmax_t Xp, std::intmax_t Yp>
+    struct mul<Xp, Yp, true>
+    {
+        static const std::intmax_t value = 1;
+    };
+
+public:
+    static const bool value = (n1 <= max / d2) && (n2 <= max / d1);
+    typedef std::ratio<mul<n1, d2, !value>::value,
+                       mul<n2, d1, !value>::value> type;
+};
+
+}  // detail
+
+// trunc towards zero
+template <class To, class Rep, class Period>
+CONSTCD11
+inline
+typename std::enable_if
+<
+    detail::no_overflow<Period, typename To::period>::value,
+    To
+>::type
+trunc(const std::chrono::duration<Rep, Period>& d)
+{
+    return To{detail::trunc(std::chrono::duration_cast<To>(d).count())};
+}
+
+template <class To, class Rep, class Period>
+CONSTCD11
+inline
+typename std::enable_if
+<
+    !detail::no_overflow<Period, typename To::period>::value,
+    To
+>::type
+trunc(const std::chrono::duration<Rep, Period>& d)
+{
+    using std::chrono::duration_cast;
+    using std::chrono::duration;
+    using rep = typename std::common_type<Rep, typename To::rep>::type;
+    return To{detail::trunc(duration_cast<To>(duration_cast<duration<rep>>(d)).count())};
+}
+
+#ifndef HAS_CHRONO_ROUNDING
+#  if defined(_MSC_FULL_VER) && (_MSC_FULL_VER >= 190023918 || (_MSC_FULL_VER >= 190000000 && defined (__clang__)))
+#    define HAS_CHRONO_ROUNDING 1
+#  elif defined(__cpp_lib_chrono) && __cplusplus > 201402 && __cpp_lib_chrono >= 201510
+#    define HAS_CHRONO_ROUNDING 1
+#  elif defined(_LIBCPP_VERSION) && __cplusplus > 201402 && _LIBCPP_VERSION >= 3800
+#    define HAS_CHRONO_ROUNDING 1
+#  else
+#    define HAS_CHRONO_ROUNDING 0
+#  endif
+#endif  // HAS_CHRONO_ROUNDING
+
+#if HAS_CHRONO_ROUNDING == 0
+
+// round down
+template <class To, class Rep, class Period>
+CONSTCD14
+inline
+typename std::enable_if
+<
+    detail::no_overflow<Period, typename To::period>::value,
+    To
+>::type
+floor(const std::chrono::duration<Rep, Period>& d)
+{
+    auto t = trunc<To>(d);
+    if (t > d)
+        return t - To{1};
+    return t;
+}
+
+template <class To, class Rep, class Period>
+CONSTCD14
+inline
+typename std::enable_if
+<
+    !detail::no_overflow<Period, typename To::period>::value,
+    To
+>::type
+floor(const std::chrono::duration<Rep, Period>& d)
+{
+    using rep = typename std::common_type<Rep, typename To::rep>::type;
+    return floor<To>(floor<std::chrono::duration<rep>>(d));
+}
+
+// round to nearest, to even on tie
+template <class To, class Rep, class Period>
+CONSTCD14
+inline
+To
+round(const std::chrono::duration<Rep, Period>& d)
+{
+    auto t0 = floor<To>(d);
+    auto t1 = t0 + To{1};
+    if (t1 == To{0} && t0 < To{0})
+        t1 = -t1;
+    auto diff0 = d - t0;
+    auto diff1 = t1 - d;
+    if (diff0 == diff1)
+    {
+        if (t0 - trunc<To>(t0/2)*2 == To{0})
+            return t0;
+        return t1;
+    }
+    if (diff0 < diff1)
+        return t0;
+    return t1;
+}
+
+// round up
+template <class To, class Rep, class Period>
+CONSTCD14
+inline
+To
+ceil(const std::chrono::duration<Rep, Period>& d)
+{
+    auto t = trunc<To>(d);
+    if (t < d)
+        return t + To{1};
+    return t;
+}
+
+template <class Rep, class Period,
+          class = typename std::enable_if
+          <
+              std::numeric_limits<Rep>::is_signed
+          >::type>
+CONSTCD11
+std::chrono::duration<Rep, Period>
+abs(std::chrono::duration<Rep, Period> d)
+{
+    return d >= d.zero() ? d : -d;
+}
+
+// round down
+template <class To, class Clock, class FromDuration>
+CONSTCD11
+inline
+std::chrono::time_point<Clock, To>
+floor(const std::chrono::time_point<Clock, FromDuration>& tp)
+{
+    using std::chrono::time_point;
+    return time_point<Clock, To>{date::floor<To>(tp.time_since_epoch())};
+}
+
+// round to nearest, to even on tie
+template <class To, class Clock, class FromDuration>
+CONSTCD11
+inline
+std::chrono::time_point<Clock, To>
+round(const std::chrono::time_point<Clock, FromDuration>& tp)
+{
+    using std::chrono::time_point;
+    return time_point<Clock, To>{round<To>(tp.time_since_epoch())};
+}
+
+// round up
+template <class To, class Clock, class FromDuration>
+CONSTCD11
+inline
+std::chrono::time_point<Clock, To>
+ceil(const std::chrono::time_point<Clock, FromDuration>& tp)
+{
+    using std::chrono::time_point;
+    return time_point<Clock, To>{ceil<To>(tp.time_since_epoch())};
+}
+
+#else  // HAS_CHRONO_ROUNDING == 1
+
+using std::chrono::floor;
+using std::chrono::ceil;
+using std::chrono::round;
+using std::chrono::abs;
+
+#endif  // HAS_CHRONO_ROUNDING
+
+// trunc towards zero
+template <class To, class Clock, class FromDuration>
+CONSTCD11
+inline
+std::chrono::time_point<Clock, To>
+trunc(const std::chrono::time_point<Clock, FromDuration>& tp)
+{
+    using std::chrono::time_point;
+    return time_point<Clock, To>{trunc<To>(tp.time_since_epoch())};
+}
+
+// day
+
+CONSTCD11 inline day::day(unsigned d) NOEXCEPT : d_(static_cast<decltype(d_)>(d)) {}
+CONSTCD14 inline day& day::operator++() NOEXCEPT {++d_; return *this;}
+CONSTCD14 inline day day::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline day& day::operator--() NOEXCEPT {--d_; return *this;}
+CONSTCD14 inline day day::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+CONSTCD14 inline day& day::operator+=(const days& d) NOEXCEPT {*this = *this + d; return *this;}
+CONSTCD14 inline day& day::operator-=(const days& d) NOEXCEPT {*this = *this - d; return *this;}
+CONSTCD11 inline day::operator unsigned() const NOEXCEPT {return d_;}
+CONSTCD11 inline bool day::ok() const NOEXCEPT {return 1 <= d_ && d_ <= 31;}
+
+CONSTCD11
+inline
+bool
+operator==(const day& x, const day& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const day& x, const day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const day& x, const day& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const day& x, const day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const day& x, const day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const day& x, const day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+days
+operator-(const day& x, const day& y) NOEXCEPT
+{
+    return days{static_cast<days::rep>(static_cast<unsigned>(x)
+                                     - static_cast<unsigned>(y))};
+}
+
+CONSTCD11
+inline
+day
+operator+(const day& x, const days& y) NOEXCEPT
+{
+    return day{static_cast<unsigned>(x) + static_cast<unsigned>(y.count())};
+}
+
+CONSTCD11
+inline
+day
+operator+(const days& x, const day& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+day
+operator-(const day& x, const days& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const day& d)
+{
+    detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::right);
+    os.width(2);
+    os << static_cast<unsigned>(d);
+    if (!d.ok())
+        os << " is not a valid day";
+    return os;
+}
+
+// month
+
+CONSTCD11 inline month::month(unsigned m) NOEXCEPT : m_(static_cast<decltype(m_)>(m)) {}
+CONSTCD14 inline month& month::operator++() NOEXCEPT {*this += months{1}; return *this;}
+CONSTCD14 inline month month::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline month& month::operator--() NOEXCEPT {*this -= months{1}; return *this;}
+CONSTCD14 inline month month::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+CONSTCD14
+inline
+month&
+month::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+month&
+month::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD11 inline month::operator unsigned() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool month::ok() const NOEXCEPT {return 1 <= m_ && m_ <= 12;}
+
+CONSTCD11
+inline
+bool
+operator==(const month& x, const month& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month& x, const month& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month& x, const month& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month& x, const month& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month& x, const month& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month& x, const month& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD14
+inline
+months
+operator-(const month& x, const month& y) NOEXCEPT
+{
+    auto const d = static_cast<unsigned>(x) - static_cast<unsigned>(y);
+    return months(d <= 11 ? d : d + 12);
+}
+
+CONSTCD14
+inline
+month
+operator+(const month& x, const months& y) NOEXCEPT
+{
+    auto const mu = static_cast<long long>(static_cast<unsigned>(x)) + (y.count() - 1);
+    auto const yr = (mu >= 0 ? mu : mu-11) / 12;
+    return month{static_cast<unsigned>(mu - yr * 12 + 1)};
+}
+
+CONSTCD14
+inline
+month
+operator+(const months& x, const month& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD14
+inline
+month
+operator-(const month& x, const months& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month& m)
+{
+    if (m.ok())
+    {
+        CharT fmt[] = {'%', 'b', 0};
+        os << format(os.getloc(), fmt, m);
+    }
+    else
+        os << static_cast<unsigned>(m) << " is not a valid month";
+    return os;
+}
+
+// year
+
+CONSTCD11 inline year::year(int y) NOEXCEPT : y_(static_cast<decltype(y_)>(y)) {}
+CONSTCD14 inline year& year::operator++() NOEXCEPT {++y_; return *this;}
+CONSTCD14 inline year year::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline year& year::operator--() NOEXCEPT {--y_; return *this;}
+CONSTCD14 inline year year::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+CONSTCD14 inline year& year::operator+=(const years& y) NOEXCEPT {*this = *this + y; return *this;}
+CONSTCD14 inline year& year::operator-=(const years& y) NOEXCEPT {*this = *this - y; return *this;}
+CONSTCD11 inline year year::operator-() const NOEXCEPT {return year{-y_};}
+CONSTCD11 inline year year::operator+() const NOEXCEPT {return *this;}
+
+CONSTCD11
+inline
+bool
+year::is_leap() const NOEXCEPT
+{
+    return y_ % 4 == 0 && (y_ % 100 != 0 || y_ % 400 == 0);
+}
+
+CONSTCD11 inline year::operator int() const NOEXCEPT {return y_;}
+
+CONSTCD11
+inline
+bool
+year::ok() const NOEXCEPT
+{
+    return y_ != std::numeric_limits<short>::min();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) == static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) < static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year& x, const year& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year& x, const year& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+years
+operator-(const year& x, const year& y) NOEXCEPT
+{
+    return years{static_cast<int>(x) - static_cast<int>(y)};
+}
+
+CONSTCD11
+inline
+year
+operator+(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) + y.count()};
+}
+
+CONSTCD11
+inline
+year
+operator+(const years& x, const year& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+year
+operator-(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) - y.count()};
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y)
+{
+    detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::internal);
+    os.width(4 + (y < year{0}));
+    os.imbue(std::locale::classic());
+    os << static_cast<int>(y);
+    if (!y.ok())
+        os << " is not a valid year";
+    return os;
+}
+
+// weekday
+
+CONSTCD14
+inline
+unsigned char
+weekday::weekday_from_days(int z) NOEXCEPT
+{
+    auto u = static_cast<unsigned>(z);
+    return static_cast<unsigned char>(z >= -4 ? (u+4) % 7 : u % 7);
+}
+
+CONSTCD11
+inline
+weekday::weekday(unsigned wd) NOEXCEPT
+    : wd_(static_cast<decltype(wd_)>(wd != 7 ? wd : 0))
+    {}
+
+CONSTCD14
+inline
+weekday::weekday(const sys_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+CONSTCD14
+inline
+weekday::weekday(const local_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+CONSTCD14 inline weekday& weekday::operator++() NOEXCEPT {*this += days{1}; return *this;}
+CONSTCD14 inline weekday weekday::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline weekday& weekday::operator--() NOEXCEPT {*this -= days{1}; return *this;}
+CONSTCD14 inline weekday weekday::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+CONSTCD14
+inline
+weekday&
+weekday::operator+=(const days& d) NOEXCEPT
+{
+    *this = *this + d;
+    return *this;
+}
+
+CONSTCD14
+inline
+weekday&
+weekday::operator-=(const days& d) NOEXCEPT
+{
+    *this = *this - d;
+    return *this;
+}
+
+CONSTCD11 inline bool weekday::ok() const NOEXCEPT {return wd_ <= 6;}
+
+CONSTCD11
+inline
+unsigned weekday::c_encoding() const NOEXCEPT
+{
+    return unsigned{wd_};
+}
+
+CONSTCD11
+inline
+unsigned weekday::iso_encoding() const NOEXCEPT
+{
+    return unsigned{((wd_ == 0u) ? 7u : wd_)};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return x.wd_ == y.wd_;
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD14
+inline
+days
+operator-(const weekday& x, const weekday& y) NOEXCEPT
+{
+    auto const wdu = x.wd_ - y.wd_;
+    auto const wk = (wdu >= 0 ? wdu : wdu-6) / 7;
+    return days{wdu - wk * 7};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const weekday& x, const days& y) NOEXCEPT
+{
+    auto const wdu = static_cast<long long>(static_cast<unsigned>(x.wd_)) + y.count();
+    auto const wk = (wdu >= 0 ? wdu : wdu-6) / 7;
+    return weekday{static_cast<unsigned>(wdu - wk * 7)};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const days& x, const weekday& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD14
+inline
+weekday
+operator-(const weekday& x, const days& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd)
+{
+    if (wd.ok())
+    {
+        CharT fmt[] = {'%', 'a', 0};
+        os << format(fmt, wd);
+    }
+    else
+        os << static_cast<unsigned>(wd.wd_) << " is not a valid weekday";
+    return os;
+}
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+inline namespace literals
+{
+
+CONSTCD11
+inline
+date::day
+operator "" _d(unsigned long long d) NOEXCEPT
+{
+    return date::day{static_cast<unsigned>(d)};
+}
+
+CONSTCD11
+inline
+date::year
+operator "" _y(unsigned long long y) NOEXCEPT
+{
+    return date::year(static_cast<int>(y));
+}
+#endif  // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+CONSTDATA date::last_spec last{};
+
+CONSTDATA date::month jan{1};
+CONSTDATA date::month feb{2};
+CONSTDATA date::month mar{3};
+CONSTDATA date::month apr{4};
+CONSTDATA date::month may{5};
+CONSTDATA date::month jun{6};
+CONSTDATA date::month jul{7};
+CONSTDATA date::month aug{8};
+CONSTDATA date::month sep{9};
+CONSTDATA date::month oct{10};
+CONSTDATA date::month nov{11};
+CONSTDATA date::month dec{12};
+
+CONSTDATA date::weekday sun{0u};
+CONSTDATA date::weekday mon{1u};
+CONSTDATA date::weekday tue{2u};
+CONSTDATA date::weekday wed{3u};
+CONSTDATA date::weekday thu{4u};
+CONSTDATA date::weekday fri{5u};
+CONSTDATA date::weekday sat{6u};
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+}  // inline namespace literals
+#endif
+
+CONSTDATA date::month January{1};
+CONSTDATA date::month February{2};
+CONSTDATA date::month March{3};
+CONSTDATA date::month April{4};
+CONSTDATA date::month May{5};
+CONSTDATA date::month June{6};
+CONSTDATA date::month July{7};
+CONSTDATA date::month August{8};
+CONSTDATA date::month September{9};
+CONSTDATA date::month October{10};
+CONSTDATA date::month November{11};
+CONSTDATA date::month December{12};
+
+CONSTDATA date::weekday Monday{1};
+CONSTDATA date::weekday Tuesday{2};
+CONSTDATA date::weekday Wednesday{3};
+CONSTDATA date::weekday Thursday{4};
+CONSTDATA date::weekday Friday{5};
+CONSTDATA date::weekday Saturday{6};
+CONSTDATA date::weekday Sunday{7};
+
+// weekday_indexed
+
+CONSTCD11
+inline
+weekday
+weekday_indexed::weekday() const NOEXCEPT
+{
+    return date::weekday{static_cast<unsigned>(wd_)};
+}
+
+CONSTCD11 inline unsigned weekday_indexed::index() const NOEXCEPT {return index_;}
+
+CONSTCD11
+inline
+bool
+weekday_indexed::ok() const NOEXCEPT
+{
+    return weekday().ok() && 1 <= index_ && index_ <= 5;
+}
+
+#ifdef __GNUC__
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wconversion"
+#endif  // __GNUC__
+
+CONSTCD11
+inline
+weekday_indexed::weekday_indexed(const date::weekday& wd, unsigned index) NOEXCEPT
+    : wd_(static_cast<decltype(wd_)>(static_cast<unsigned>(wd.wd_)))
+    , index_(static_cast<decltype(index_)>(index))
+    {}
+
+#ifdef __GNUC__
+#  pragma GCC diagnostic pop
+#endif  // __GNUC__
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_indexed& wdi)
+{
+    os << wdi.weekday() << '[' << wdi.index();
+    if (!(1 <= wdi.index() && wdi.index() <= 5))
+        os << " is not a valid index";
+    os << ']';
+    return os;
+}
+
+CONSTCD11
+inline
+weekday_indexed
+weekday::operator[](unsigned index) const NOEXCEPT
+{
+    return {*this, index};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT
+{
+    return x.weekday() == y.weekday() && x.index() == y.index();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+// weekday_last
+
+CONSTCD11 inline date::weekday weekday_last::weekday() const NOEXCEPT {return wd_;}
+CONSTCD11 inline bool weekday_last::ok() const NOEXCEPT {return wd_.ok();}
+CONSTCD11 inline weekday_last::weekday_last(const date::weekday& wd) NOEXCEPT : wd_(wd) {}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday_last& x, const weekday_last& y) NOEXCEPT
+{
+    return x.weekday() == y.weekday();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday_last& x, const weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_last& wdl)
+{
+    return os << wdl.weekday() << "[last]";
+}
+
+CONSTCD11
+inline
+weekday_last
+weekday::operator[](last_spec) const NOEXCEPT
+{
+    return weekday_last{*this};
+}
+
+// year_month
+
+CONSTCD11
+inline
+year_month::year_month(const date::year& y, const date::month& m) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    {}
+
+CONSTCD11 inline year year_month::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool year_month::ok() const NOEXCEPT {return y_.ok() && m_.ok();}
+
+template<class>
+CONSTCD14
+inline
+year_month&
+year_month::operator+=(const months& dm) NOEXCEPT
+{
+    *this = *this + dm;
+    return *this;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month&
+year_month::operator-=(const months& dm) NOEXCEPT
+{
+    *this = *this - dm;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator+=(const years& dy) NOEXCEPT
+{
+    *this = *this + dy;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator-=(const years& dy) NOEXCEPT
+{
+    *this = *this - dy;
+    return *this;
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month() < y.month()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class>
+CONSTCD14
+inline
+year_month
+operator+(const year_month& ym, const months& dm) NOEXCEPT
+{
+    auto dmi = static_cast<int>(static_cast<unsigned>(ym.month())) - 1 + dm.count();
+    auto dy = (dmi >= 0 ? dmi : dmi-11) / 12;
+    dmi = dmi - dy * 12 + 1;
+    return (ym.year() + years(dy)) / month(static_cast<unsigned>(dmi));
+}
+
+template<class>
+CONSTCD14
+inline
+year_month
+operator+(const months& dm, const year_month& ym) NOEXCEPT
+{
+    return ym + dm;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month
+operator-(const year_month& ym, const months& dm) NOEXCEPT
+{
+    return ym + -dm;
+}
+
+CONSTCD11
+inline
+months
+operator-(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return (x.year() - y.year()) +
+            months(static_cast<unsigned>(x.month()) - static_cast<unsigned>(y.month()));
+}
+
+CONSTCD11
+inline
+year_month
+operator+(const year_month& ym, const years& dy) NOEXCEPT
+{
+    return (ym.year() + dy) / ym.month();
+}
+
+CONSTCD11
+inline
+year_month
+operator+(const years& dy, const year_month& ym) NOEXCEPT
+{
+    return ym + dy;
+}
+
+CONSTCD11
+inline
+year_month
+operator-(const year_month& ym, const years& dy) NOEXCEPT
+{
+    return ym + -dy;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month& ym)
+{
+    return os << ym.year() << '/' << ym.month();
+}
+
+// month_day
+
+CONSTCD11
+inline
+month_day::month_day(const date::month& m, const date::day& d) NOEXCEPT
+    : m_(m)
+    , d_(d)
+    {}
+
+CONSTCD11 inline date::month month_day::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline date::day month_day::day() const NOEXCEPT {return d_;}
+
+CONSTCD14
+inline
+bool
+month_day::ok() const NOEXCEPT
+{
+    CONSTDATA date::day d[] =
+    {
+        date::day(31), date::day(29), date::day(31),
+        date::day(30), date::day(31), date::day(30),
+        date::day(31), date::day(31), date::day(30),
+        date::day(31), date::day(30), date::day(31)
+    };
+    return m_.ok() && date::day{1} <= d_ && d_ <= d[static_cast<unsigned>(m_)-1];
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.day() == y.day();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return x.month() < y.month() ? true
+        : (x.month() > y.month() ? false
+        : (x.day() < y.day()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day& md)
+{
+    return os << md.month() << '/' << md.day();
+}
+
+// month_day_last
+
+CONSTCD11 inline month month_day_last::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool month_day_last::ok() const NOEXCEPT {return m_.ok();}
+CONSTCD11 inline month_day_last::month_day_last(const date::month& m) NOEXCEPT : m_(m) {}
+
+CONSTCD11
+inline
+bool
+operator==(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return x.month() == y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return x.month() < y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day_last& mdl)
+{
+    return os << mdl.month() << "/last";
+}
+
+// month_weekday
+
+CONSTCD11
+inline
+month_weekday::month_weekday(const date::month& m,
+                             const date::weekday_indexed& wdi) NOEXCEPT
+    : m_(m)
+    , wdi_(wdi)
+    {}
+
+CONSTCD11 inline month month_weekday::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday_indexed
+month_weekday::weekday_indexed() const NOEXCEPT
+{
+    return wdi_;
+}
+
+CONSTCD11
+inline
+bool
+month_weekday::ok() const NOEXCEPT
+{
+    return m_.ok() && wdi_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_weekday& x, const month_weekday& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.weekday_indexed() == y.weekday_indexed();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_weekday& x, const month_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday& mwd)
+{
+    return os << mwd.month() << '/' << mwd.weekday_indexed();
+}
+
+// month_weekday_last
+
+CONSTCD11
+inline
+month_weekday_last::month_weekday_last(const date::month& m,
+                                       const date::weekday_last& wdl) NOEXCEPT
+    : m_(m)
+    , wdl_(wdl)
+    {}
+
+CONSTCD11 inline month month_weekday_last::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday_last
+month_weekday_last::weekday_last() const NOEXCEPT
+{
+    return wdl_;
+}
+
+CONSTCD11
+inline
+bool
+month_weekday_last::ok() const NOEXCEPT
+{
+    return m_.ok() && wdl_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.weekday_last() == y.weekday_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday_last& mwdl)
+{
+    return os << mwdl.month() << '/' << mwdl.weekday_last();
+}
+
+// year_month_day_last
+
+CONSTCD11
+inline
+year_month_day_last::year_month_day_last(const date::year& y,
+                                         const date::month_day_last& mdl) NOEXCEPT
+    : y_(y)
+    , mdl_(mdl)
+    {}
+
+template<class>
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_day_last::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_day_last::month() const NOEXCEPT {return mdl_.month();}
+
+CONSTCD11
+inline
+month_day_last
+year_month_day_last::month_day_last() const NOEXCEPT
+{
+    return mdl_;
+}
+
+CONSTCD14
+inline
+day
+year_month_day_last::day() const NOEXCEPT
+{
+    CONSTDATA date::day d[] =
+    {
+        date::day(31), date::day(28), date::day(31),
+        date::day(30), date::day(31), date::day(30),
+        date::day(31), date::day(31), date::day(30),
+        date::day(31), date::day(30), date::day(31)
+    };
+    return (month() != February || !y_.is_leap()) && mdl_.ok() ?
+        d[static_cast<unsigned>(month()) - 1] : date::day{29};
+}
+
+CONSTCD14
+inline
+year_month_day_last::operator sys_days() const NOEXCEPT
+{
+    return sys_days(year()/month()/day());
+}
+
+CONSTCD14
+inline
+year_month_day_last::operator local_days() const NOEXCEPT
+{
+    return local_days(year()/month()/day());
+}
+
+CONSTCD11
+inline
+bool
+year_month_day_last::ok() const NOEXCEPT
+{
+    return y_.ok() && mdl_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month_day_last() == y.month_day_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month_day_last() < y.month_day_last()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day_last& ymdl)
+{
+    return os << ymdl.year() << '/' << ymdl.month_day_last();
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const months& dm) NOEXCEPT
+{
+    return (ymdl.year() / ymdl.month() + dm) / last;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day_last
+operator+(const months& dm, const year_month_day_last& ymdl) NOEXCEPT
+{
+    return ymdl + dm;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const months& dm) NOEXCEPT
+{
+    return ymdl + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const years& dy) NOEXCEPT
+{
+    return {ymdl.year()+dy, ymdl.month_day_last()};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator+(const years& dy, const year_month_day_last& ymdl) NOEXCEPT
+{
+    return ymdl + dy;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const years& dy) NOEXCEPT
+{
+    return ymdl + (-dy);
+}
+
+// year_month_day
+
+CONSTCD11
+inline
+year_month_day::year_month_day(const date::year& y, const date::month& m,
+                               const date::day& d) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , d_(d)
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(const year_month_day_last& ymdl) NOEXCEPT
+    : y_(ymdl.year())
+    , m_(ymdl.month())
+    , d_(ymdl.day())
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(sys_days dp) NOEXCEPT
+    : year_month_day(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(local_days dp) NOEXCEPT
+    : year_month_day(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD11 inline year year_month_day::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_day::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline day year_month_day::day() const NOEXCEPT {return d_;}
+
+template<class>
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD14
+inline
+days
+year_month_day::to_days() const NOEXCEPT
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18,
+             "This algorithm has not been ported to a 16 bit unsigned integer");
+    static_assert(std::numeric_limits<int>::digits >= 20,
+             "This algorithm has not been ported to a 16 bit signed integer");
+    auto const y = static_cast<int>(y_) - (m_ <= February);
+    auto const m = static_cast<unsigned>(m_);
+    auto const d = static_cast<unsigned>(d_);
+    auto const era = (y >= 0 ? y : y-399) / 400;
+    auto const yoe = static_cast<unsigned>(y - era * 400);       // [0, 399]
+    auto const doy = (153*(m > 2 ? m-3 : m+9) + 2)/5 + d-1;      // [0, 365]
+    auto const doe = yoe * 365 + yoe/4 - yoe/100 + doy;          // [0, 146096]
+    return days{era * 146097 + static_cast<int>(doe) - 719468};
+}
+
+CONSTCD14
+inline
+year_month_day::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_day::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD14
+inline
+bool
+year_month_day::ok() const NOEXCEPT
+{
+    if (!(y_.ok() && m_.ok()))
+        return false;
+    return date::day{1} <= d_ && d_ <= (y_ / m_ / last).day();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() && x.day() == y.day();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month() < y.month() ? true
+        : (x.month() > y.month() ? false
+        : (x.day() < y.day()))));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day& ymd)
+{
+    detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::right);
+    os.imbue(std::locale::classic());
+    os << ymd.year() << '-';
+    os.width(2);
+    os << static_cast<unsigned>(ymd.month()) << '-';
+    os << ymd.day();
+    if (!ymd.ok())
+        os << " is not a valid date";
+    return os;
+}
+
+CONSTCD14
+inline
+year_month_day
+year_month_day::from_days(days dp) NOEXCEPT
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18,
+             "This algorithm has not been ported to a 16 bit unsigned integer");
+    static_assert(std::numeric_limits<int>::digits >= 20,
+             "This algorithm has not been ported to a 16 bit signed integer");
+    auto const z = dp.count() + 719468;
+    auto const era = (z >= 0 ? z : z - 146096) / 146097;
+    auto const doe = static_cast<unsigned>(z - era * 146097);          // [0, 146096]
+    auto const yoe = (doe - doe/1460 + doe/36524 - doe/146096) / 365;  // [0, 399]
+    auto const y = static_cast<days::rep>(yoe) + era * 400;
+    auto const doy = doe - (365*yoe + yoe/4 - yoe/100);                // [0, 365]
+    auto const mp = (5*doy + 2)/153;                                   // [0, 11]
+    auto const d = doy - (153*mp+2)/5 + 1;                             // [1, 31]
+    auto const m = mp < 10 ? mp+3 : mp-9;                              // [1, 12]
+    return year_month_day{date::year{y + (m <= 2)}, date::month(m), date::day(d)};
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day
+operator+(const year_month_day& ymd, const months& dm) NOEXCEPT
+{
+    return (ymd.year() / ymd.month() + dm) / ymd.day();
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day
+operator+(const months& dm, const year_month_day& ymd) NOEXCEPT
+{
+    return ymd + dm;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_day
+operator-(const year_month_day& ymd, const months& dm) NOEXCEPT
+{
+    return ymd + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_day
+operator+(const year_month_day& ymd, const years& dy) NOEXCEPT
+{
+    return (ymd.year() + dy) / ymd.month() / ymd.day();
+}
+
+CONSTCD11
+inline
+year_month_day
+operator+(const years& dy, const year_month_day& ymd) NOEXCEPT
+{
+    return ymd + dy;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator-(const year_month_day& ymd, const years& dy) NOEXCEPT
+{
+    return ymd + (-dy);
+}
+
+// year_month_weekday
+
+CONSTCD11
+inline
+year_month_weekday::year_month_weekday(const date::year& y, const date::month& m,
+                                       const date::weekday_indexed& wdi)
+        NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , wdi_(wdi)
+    {}
+
+CONSTCD14
+inline
+year_month_weekday::year_month_weekday(const sys_days& dp) NOEXCEPT
+    : year_month_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_weekday::year_month_weekday(const local_days& dp) NOEXCEPT
+    : year_month_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_weekday::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_weekday::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday
+year_month_weekday::weekday() const NOEXCEPT
+{
+    return wdi_.weekday();
+}
+
+CONSTCD11
+inline
+unsigned
+year_month_weekday::index() const NOEXCEPT
+{
+    return wdi_.index();
+}
+
+CONSTCD11
+inline
+weekday_indexed
+year_month_weekday::weekday_indexed() const NOEXCEPT
+{
+    return wdi_;
+}
+
+CONSTCD14
+inline
+year_month_weekday::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_weekday::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD14
+inline
+bool
+year_month_weekday::ok() const NOEXCEPT
+{
+    if (!y_.ok() || !m_.ok() || !wdi_.weekday().ok() || wdi_.index() < 1)
+        return false;
+    if (wdi_.index() <= 4)
+        return true;
+    auto d2 = wdi_.weekday() - date::weekday(static_cast<sys_days>(y_/m_/1)) +
+                  days((wdi_.index()-1)*7 + 1);
+    return static_cast<unsigned>(d2.count()) <= static_cast<unsigned>((y_/m_/last).day());
+}
+
+CONSTCD14
+inline
+year_month_weekday
+year_month_weekday::from_days(days d) NOEXCEPT
+{
+    sys_days dp{d};
+    auto const wd = date::weekday(dp);
+    auto const ymd = year_month_day(dp);
+    return {ymd.year(), ymd.month(), wd[(static_cast<unsigned>(ymd.day())-1)/7+1]};
+}
+
+CONSTCD14
+inline
+days
+year_month_weekday::to_days() const NOEXCEPT
+{
+    auto d = sys_days(y_/m_/1);
+    return (d + (wdi_.weekday() - date::weekday(d) + days{(wdi_.index()-1)*7})
+           ).time_since_epoch();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() &&
+           x.weekday_indexed() == y.weekday_indexed();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday& ymwdi)
+{
+    return os << ymwdi.year() << '/' << ymwdi.month()
+              << '/' << ymwdi.weekday_indexed();
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const months& dm) NOEXCEPT
+{
+    return (ymwd.year() / ymwd.month() + dm) / ymwd.weekday_indexed();
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday
+operator+(const months& dm, const year_month_weekday& ymwd) NOEXCEPT
+{
+    return ymwd + dm;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const months& dm) NOEXCEPT
+{
+    return ymwd + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const years& dy) NOEXCEPT
+{
+    return {ymwd.year()+dy, ymwd.month(), ymwd.weekday_indexed()};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator+(const years& dy, const year_month_weekday& ymwd) NOEXCEPT
+{
+    return ymwd + dy;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const years& dy) NOEXCEPT
+{
+    return ymwd + (-dy);
+}
+
+// year_month_weekday_last
+
+CONSTCD11
+inline
+year_month_weekday_last::year_month_weekday_last(const date::year& y,
+                                                 const date::month& m,
+                                                 const date::weekday_last& wdl) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , wdl_(wdl)
+    {}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_weekday_last::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_weekday_last::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday
+year_month_weekday_last::weekday() const NOEXCEPT
+{
+    return wdl_.weekday();
+}
+
+CONSTCD11
+inline
+weekday_last
+year_month_weekday_last::weekday_last() const NOEXCEPT
+{
+    return wdl_;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_weekday_last::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD11
+inline
+bool
+year_month_weekday_last::ok() const NOEXCEPT
+{
+    return y_.ok() && m_.ok() && wdl_.ok();
+}
+
+CONSTCD14
+inline
+days
+year_month_weekday_last::to_days() const NOEXCEPT
+{
+    auto const d = sys_days(y_/m_/last);
+    return (d - (date::weekday{d} - wdl_.weekday())).time_since_epoch();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() &&
+           x.weekday_last() == y.weekday_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday_last& ymwdl)
+{
+    return os << ymwdl.year() << '/' << ymwdl.month() << '/' << ymwdl.weekday_last();
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT
+{
+    return (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last();
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday_last
+operator+(const months& dm, const year_month_weekday_last& ymwdl) NOEXCEPT
+{
+    return ymwdl + dm;
+}
+
+template<class>
+CONSTCD14
+inline
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT
+{
+    return ymwdl + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT
+{
+    return {ymwdl.year()+dy, ymwdl.month(), ymwdl.weekday_last()};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator+(const years& dy, const year_month_weekday_last& ymwdl) NOEXCEPT
+{
+    return ymwdl + dy;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT
+{
+    return ymwdl + (-dy);
+}
+
+// year_month from operator/()
+
+CONSTCD11
+inline
+year_month
+operator/(const year& y, const month& m) NOEXCEPT
+{
+    return {y, m};
+}
+
+CONSTCD11
+inline
+year_month
+operator/(const year& y, int   m) NOEXCEPT
+{
+    return y / month(static_cast<unsigned>(m));
+}
+
+// month_day from operator/()
+
+CONSTCD11
+inline
+month_day
+operator/(const month& m, const day& d) NOEXCEPT
+{
+    return {m, d};
+}
+
+CONSTCD11
+inline
+month_day
+operator/(const day& d, const month& m) NOEXCEPT
+{
+    return m / d;
+}
+
+CONSTCD11
+inline
+month_day
+operator/(const month& m, int d) NOEXCEPT
+{
+    return m / day(static_cast<unsigned>(d));
+}
+
+CONSTCD11
+inline
+month_day
+operator/(int m, const day& d) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / d;
+}
+
+CONSTCD11 inline month_day operator/(const day& d, int m) NOEXCEPT {return m / d;}
+
+// month_day_last from operator/()
+
+CONSTCD11
+inline
+month_day_last
+operator/(const month& m, last_spec) NOEXCEPT
+{
+    return month_day_last{m};
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(last_spec, const month& m) NOEXCEPT
+{
+    return m/last;
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(int m, last_spec) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m))/last;
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(last_spec, int m) NOEXCEPT
+{
+    return m/last;
+}
+
+// month_weekday from operator/()
+
+CONSTCD11
+inline
+month_weekday
+operator/(const month& m, const weekday_indexed& wdi) NOEXCEPT
+{
+    return {m, wdi};
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(const weekday_indexed& wdi, const month& m) NOEXCEPT
+{
+    return m / wdi;
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(int m, const weekday_indexed& wdi) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / wdi;
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(const weekday_indexed& wdi, int m) NOEXCEPT
+{
+    return m / wdi;
+}
+
+// month_weekday_last from operator/()
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const month& m, const weekday_last& wdl) NOEXCEPT
+{
+    return {m, wdl};
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const weekday_last& wdl, const month& m) NOEXCEPT
+{
+    return m / wdl;
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(int m, const weekday_last& wdl) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / wdl;
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const weekday_last& wdl, int m) NOEXCEPT
+{
+    return m / wdl;
+}
+
+// year_month_day from operator/()
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year_month& ym, const day& d) NOEXCEPT
+{
+    return {ym.year(), ym.month(), d};
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year_month& ym, int d)  NOEXCEPT
+{
+    return ym / day(static_cast<unsigned>(d));
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year& y, const month_day& md) NOEXCEPT
+{
+    return y / md.month() / md.day();
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(int y, const month_day& md) NOEXCEPT
+{
+    return year(y) / md;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const month_day& md, const year& y)  NOEXCEPT
+{
+    return y / md;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const month_day& md, int y) NOEXCEPT
+{
+    return year(y) / md;
+}
+
+// year_month_day_last from operator/()
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const year_month& ym, last_spec) NOEXCEPT
+{
+    return {ym.year(), month_day_last{ym.month()}};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const year& y, const month_day_last& mdl) NOEXCEPT
+{
+    return {y, mdl};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(int y, const month_day_last& mdl) NOEXCEPT
+{
+    return year(y) / mdl;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const month_day_last& mdl, const year& y) NOEXCEPT
+{
+    return y / mdl;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const month_day_last& mdl, int y) NOEXCEPT
+{
+    return year(y) / mdl;
+}
+
+// year_month_weekday from operator/()
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const year_month& ym, const weekday_indexed& wdi) NOEXCEPT
+{
+    return {ym.year(), ym.month(), wdi};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const year& y, const month_weekday& mwd) NOEXCEPT
+{
+    return {y, mwd.month(), mwd.weekday_indexed()};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(int y, const month_weekday& mwd) NOEXCEPT
+{
+    return year(y) / mwd;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const month_weekday& mwd, const year& y) NOEXCEPT
+{
+    return y / mwd;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const month_weekday& mwd, int y) NOEXCEPT
+{
+    return year(y) / mwd;
+}
+
+// year_month_weekday_last from operator/()
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const year_month& ym, const weekday_last& wdl) NOEXCEPT
+{
+    return {ym.year(), ym.month(), wdl};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const year& y, const month_weekday_last& mwdl) NOEXCEPT
+{
+    return {y, mwdl.month(), mwdl.weekday_last()};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(int y, const month_weekday_last& mwdl) NOEXCEPT
+{
+    return year(y) / mwdl;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, const year& y) NOEXCEPT
+{
+    return y / mwdl;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, int y) NOEXCEPT
+{
+    return year(y) / mwdl;
+}
+
+template <class Duration>
+struct fields;
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const fields<Duration>& fds, const std::string* abbrev = nullptr,
+          const std::chrono::seconds* offset_sec = nullptr);
+
+template <class CharT, class Traits, class Duration, class Alloc>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            fields<Duration>& fds, std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr);
+
+// hh_mm_ss
+
+namespace detail
+{
+
+struct undocumented {explicit undocumented() = default;};
+
+// width<n>::value is the number of fractional decimal digits in 1/n
+// width<0>::value and width<1>::value are defined to be 0
+// If 1/n takes more than 18 fractional decimal digits,
+//   the result is truncated to 19.
+// Example:  width<2>::value    ==  1
+// Example:  width<3>::value    == 19
+// Example:  width<4>::value    ==  2
+// Example:  width<10>::value   ==  1
+// Example:  width<1000>::value ==  3
+template <std::uint64_t n, std::uint64_t d = 10, unsigned w = 0,
+          bool should_continue = !(n < 2) && d != 0 && (w < 19)>
+struct width
+{
+    static CONSTDATA unsigned value = 1 + width<n, d%n*10, w+1>::value;
+};
+
+template <std::uint64_t n, std::uint64_t d, unsigned w>
+struct width<n, d, w, false>
+{
+    static CONSTDATA unsigned value = 0;
+};
+
+template <unsigned exp>
+struct static_pow10
+{
+private:
+    static CONSTDATA std::uint64_t h = static_pow10<exp/2>::value;
+public:
+    static CONSTDATA std::uint64_t value = h * h * (exp % 2 ? 10 : 1);
+};
+
+template <>
+struct static_pow10<0>
+{
+    static CONSTDATA std::uint64_t value = 1;
+};
+
+template <class Duration>
+class decimal_format_seconds
+{
+    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
+    using rep = typename CT::rep;
+public:
+    static unsigned constexpr width = detail::width<CT::period::den>::value < 19 ?
+                                      detail::width<CT::period::den>::value : 6u;
+    using precision = std::chrono::duration<rep,
+                                            std::ratio<1, static_pow10<width>::value>>;
+
+private:
+    std::chrono::seconds s_;
+    precision            sub_s_;
+
+public:
+    CONSTCD11 decimal_format_seconds()
+        : s_()
+        , sub_s_()
+        {}
+
+    CONSTCD11 explicit decimal_format_seconds(const Duration& d) NOEXCEPT
+        : s_(std::chrono::duration_cast<std::chrono::seconds>(d))
+        , sub_s_(std::chrono::treat_as_floating_point<rep>::value ? d - s_ :
+                     std::chrono::duration_cast<precision>(d - s_))
+        {}
+
+    CONSTCD14 std::chrono::seconds& seconds() NOEXCEPT {return s_;}
+    CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT {return s_;}
+    CONSTCD11 precision subseconds() const NOEXCEPT {return sub_s_;}
+
+    CONSTCD14 precision to_duration() const NOEXCEPT
+    {
+        return s_ + sub_s_;
+    }
+
+    CONSTCD11 bool in_conventional_range() const NOEXCEPT
+    {
+        return sub_s_ < std::chrono::seconds{1} && s_ < std::chrono::minutes{1};
+    }
+
+    template <class CharT, class Traits>
+    friend
+    std::basic_ostream<CharT, Traits>&
+    operator<<(std::basic_ostream<CharT, Traits>& os, const decimal_format_seconds& x)
+    {
+        return x.print(os, std::chrono::treat_as_floating_point<rep>{});
+    }
+
+    template <class CharT, class Traits>
+    std::basic_ostream<CharT, Traits>&
+    print(std::basic_ostream<CharT, Traits>& os, std::true_type) const
+    {
+        date::detail::save_ostream<CharT, Traits> _(os);
+        std::chrono::duration<rep> d = s_ + sub_s_;
+        if (d < std::chrono::seconds{10})
+            os << '0';
+        os << std::fixed << d.count();
+        return os;
+    }
+
+    template <class CharT, class Traits>
+    std::basic_ostream<CharT, Traits>&
+    print(std::basic_ostream<CharT, Traits>& os, std::false_type) const
+    {
+        date::detail::save_ostream<CharT, Traits> _(os);
+        os.fill('0');
+        os.flags(std::ios::dec | std::ios::right);
+        os.width(2);
+        os << s_.count();
+        if (width > 0)
+        {
+#if !ONLY_C_LOCALE
+            os << std::use_facet<std::numpunct<CharT>>(os.getloc()).decimal_point();
+#else
+            os << '.';
+#endif
+            date::detail::save_ostream<CharT, Traits> _s(os);
+            os.imbue(std::locale::classic());
+            os.width(width);
+            os << sub_s_.count();
+        }
+        return os;
+    }
+};
+
+template <class Rep, class Period>
+inline
+CONSTCD11
+typename std::enable_if
+         <
+            std::numeric_limits<Rep>::is_signed,
+            std::chrono::duration<Rep, Period>
+         >::type
+abs(std::chrono::duration<Rep, Period> d)
+{
+    return d >= d.zero() ? +d : -d;
+}
+
+template <class Rep, class Period>
+inline
+CONSTCD11
+typename std::enable_if
+         <
+            !std::numeric_limits<Rep>::is_signed,
+            std::chrono::duration<Rep, Period>
+         >::type
+abs(std::chrono::duration<Rep, Period> d)
+{
+    return d;
+}
+
+}  // namespace detail
+
+template <class Duration>
+class hh_mm_ss
+{
+    using dfs = detail::decimal_format_seconds<typename std::common_type<Duration,
+                                               std::chrono::seconds>::type>;
+
+    std::chrono::hours h_;
+    std::chrono::minutes m_;
+    dfs s_;
+    bool neg_;
+
+public:
+    static unsigned CONSTDATA fractional_width = dfs::width;
+    using precision = typename dfs::precision;
+
+    CONSTCD11 hh_mm_ss() NOEXCEPT
+        : hh_mm_ss(Duration::zero())
+        {}
+
+    CONSTCD11 explicit hh_mm_ss(Duration d) NOEXCEPT
+        : h_(std::chrono::duration_cast<std::chrono::hours>(detail::abs(d)))
+        , m_(std::chrono::duration_cast<std::chrono::minutes>(detail::abs(d)) - h_)
+        , s_(detail::abs(d) - h_ - m_)
+        , neg_(d < Duration::zero())
+        {}
+
+    CONSTCD11 std::chrono::hours hours() const NOEXCEPT {return h_;}
+    CONSTCD11 std::chrono::minutes minutes() const NOEXCEPT {return m_;}
+    CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT {return s_.seconds();}
+    CONSTCD14 std::chrono::seconds&
+        seconds(detail::undocumented) NOEXCEPT {return s_.seconds();}
+    CONSTCD11 precision subseconds() const NOEXCEPT {return s_.subseconds();}
+    CONSTCD11 bool is_negative() const NOEXCEPT {return neg_;}
+
+    CONSTCD11 explicit operator  precision()   const NOEXCEPT {return to_duration();}
+    CONSTCD11          precision to_duration() const NOEXCEPT
+        {return (s_.to_duration() + m_ + h_) * (1-2*neg_);}
+
+    CONSTCD11 bool in_conventional_range() const NOEXCEPT
+    {
+        return !neg_ && h_ < days{1} && m_ < std::chrono::hours{1} &&
+               s_.in_conventional_range();
+    }
+
+private:
+
+    template <class charT, class traits>
+    friend
+    std::basic_ostream<charT, traits>&
+    operator<<(std::basic_ostream<charT, traits>& os, hh_mm_ss const& tod)
+    {
+        if (tod.is_negative())
+            os << '-';
+        if (tod.h_ < std::chrono::hours{10})
+            os << '0';
+        os << tod.h_.count() << ':';
+        if (tod.m_ < std::chrono::minutes{10})
+            os << '0';
+        os << tod.m_.count() << ':' << tod.s_;
+        return os;
+    }
+
+    template <class CharT, class Traits, class Duration2>
+    friend
+    std::basic_ostream<CharT, Traits>&
+    date::to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const fields<Duration2>& fds, const std::string* abbrev,
+          const std::chrono::seconds* offset_sec);
+
+    template <class CharT, class Traits, class Duration2, class Alloc>
+    friend
+    std::basic_istream<CharT, Traits>&
+    date::from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+          fields<Duration2>& fds,
+          std::basic_string<CharT, Traits, Alloc>* abbrev, std::chrono::minutes* offset);
+};
+
+inline
+CONSTCD14
+bool
+is_am(std::chrono::hours const& h) NOEXCEPT
+{
+    using std::chrono::hours;
+    return hours{0} <= h && h < hours{12};
+}
+
+inline
+CONSTCD14
+bool
+is_pm(std::chrono::hours const& h) NOEXCEPT
+{
+    using std::chrono::hours;
+    return hours{12} <= h && h < hours{24};
+}
+
+inline
+CONSTCD14
+std::chrono::hours
+make12(std::chrono::hours h) NOEXCEPT
+{
+    using std::chrono::hours;
+    if (h < hours{12})
+    {
+        if (h == hours{0})
+            h = hours{12};
+    }
+    else
+    {
+        if (h != hours{12})
+            h = h - hours{12};
+    }
+    return h;
+}
+
+inline
+CONSTCD14
+std::chrono::hours
+make24(std::chrono::hours h, bool is_pm) NOEXCEPT
+{
+    using std::chrono::hours;
+    if (is_pm)
+    {
+        if (h != hours{12})
+            h = h + hours{12};
+    }
+    else if (h == hours{12})
+        h = hours{0};
+    return h;
+}
+
+template <class Duration>
+using time_of_day = hh_mm_ss<Duration>;
+
+template <class Rep, class Period,
+          class = typename std::enable_if
+              <!std::chrono::treat_as_floating_point<Rep>::value>::type>
+CONSTCD11
+inline
+hh_mm_ss<std::chrono::duration<Rep, Period>>
+make_time(const std::chrono::duration<Rep, Period>& d)
+{
+    return hh_mm_ss<std::chrono::duration<Rep, Period>>(d);
+}
+
+template <class CharT, class Traits, class Duration>
+inline
+typename std::enable_if
+<
+    !std::chrono::treat_as_floating_point<typename Duration::rep>::value &&
+        std::ratio_less<typename Duration::period, days::period>::value
+    , std::basic_ostream<CharT, Traits>&
+>::type
+operator<<(std::basic_ostream<CharT, Traits>& os, const sys_time<Duration>& tp)
+{
+    auto const dp = date::floor<days>(tp);
+    return os << year_month_day(dp) << ' ' << make_time(tp-dp);
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const sys_days& dp)
+{
+    return os << year_month_day(dp);
+}
+
+template <class CharT, class Traits, class Duration>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const local_time<Duration>& ut)
+{
+    return (os << sys_time<Duration>{ut.time_since_epoch()});
+}
+
+namespace detail
+{
+
+template <class CharT, std::size_t N>
+class string_literal;
+
+template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
+inline
+CONSTCD14
+string_literal<typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type,
+               N1 + N2 - 1>
+operator+(const string_literal<CharT1, N1>& x, const string_literal<CharT2, N2>& y) NOEXCEPT;
+
+template <class CharT, std::size_t N>
+class string_literal
+{
+    CharT p_[N];
+
+    CONSTCD11 string_literal() NOEXCEPT
+      : p_{}
+    {}
+
+public:
+    using const_iterator = const CharT*;
+
+    string_literal(string_literal const&) = default;
+    string_literal& operator=(string_literal const&) = delete;
+
+    template <std::size_t N1 = 2,
+              class = typename std::enable_if<N1 == N>::type>
+    CONSTCD11 string_literal(CharT c) NOEXCEPT
+        : p_{c}
+    {
+    }
+
+    template <std::size_t N1 = 3,
+              class = typename std::enable_if<N1 == N>::type>
+    CONSTCD11 string_literal(CharT c1, CharT c2) NOEXCEPT
+        : p_{c1, c2}
+    {
+    }
+
+    template <std::size_t N1 = 4,
+              class = typename std::enable_if<N1 == N>::type>
+    CONSTCD11 string_literal(CharT c1, CharT c2, CharT c3) NOEXCEPT
+        : p_{c1, c2, c3}
+    {
+    }
+
+    CONSTCD14 string_literal(const CharT(&a)[N]) NOEXCEPT
+        : p_{}
+    {
+        for (std::size_t i = 0; i < N; ++i)
+            p_[i] = a[i];
+    }
+
+    template <class U = CharT,
+              class = typename std::enable_if<(1 < sizeof(U))>::type>
+    CONSTCD14 string_literal(const char(&a)[N]) NOEXCEPT
+        : p_{}
+    {
+        for (std::size_t i = 0; i < N; ++i)
+            p_[i] = a[i];
+    }
+
+    template <class CharT2,
+              class = typename std::enable_if<!std::is_same<CharT2, CharT>::value>::type>
+    CONSTCD14 string_literal(string_literal<CharT2, N> const& a) NOEXCEPT
+        : p_{}
+    {
+        for (std::size_t i = 0; i < N; ++i)
+            p_[i] = a[i];
+    }
+
+    CONSTCD11 const CharT* data() const NOEXCEPT {return p_;}
+    CONSTCD11 std::size_t size() const NOEXCEPT {return N-1;}
+
+    CONSTCD11 const_iterator begin() const NOEXCEPT {return p_;}
+    CONSTCD11 const_iterator end()   const NOEXCEPT {return p_ + N-1;}
+
+    CONSTCD11 CharT const& operator[](std::size_t n) const NOEXCEPT
+    {
+        return p_[n];
+    }
+
+    template <class Traits>
+    friend
+    std::basic_ostream<CharT, Traits>&
+    operator<<(std::basic_ostream<CharT, Traits>& os, const string_literal& s)
+    {
+        return os << s.p_;
+    }
+
+    template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
+    friend
+    CONSTCD14
+    string_literal<typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type,
+                   N1 + N2 - 1>
+    operator+(const string_literal<CharT1, N1>& x, const string_literal<CharT2, N2>& y) NOEXCEPT;
+};
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 3>
+operator+(const string_literal<CharT, 2>& x, const string_literal<CharT, 2>& y) NOEXCEPT
+{
+  return string_literal<CharT, 3>(x[0], y[0]);
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 4>
+operator+(const string_literal<CharT, 3>& x, const string_literal<CharT, 2>& y) NOEXCEPT
+{
+  return string_literal<CharT, 4>(x[0], x[1], y[0]);
+}
+
+template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
+CONSTCD14
+inline
+string_literal<typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type,
+               N1 + N2 - 1>
+operator+(const string_literal<CharT1, N1>& x, const string_literal<CharT2, N2>& y) NOEXCEPT
+{
+    using CT = typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type;
+
+    string_literal<CT, N1 + N2 - 1> r;
+    std::size_t i = 0;
+    for (; i < N1-1; ++i)
+       r.p_[i] = CT(x.p_[i]);
+    for (std::size_t j = 0; j < N2; ++j, ++i)
+       r.p_[i] = CT(y.p_[j]);
+
+    return r;
+}
+
+
+template <class CharT, class Traits, class Alloc, std::size_t N>
+inline
+std::basic_string<CharT, Traits, Alloc>
+operator+(std::basic_string<CharT, Traits, Alloc> x, const string_literal<CharT, N>& y)
+{
+    x.append(y.data(), y.size());
+    return x;
+}
+
+#if __cplusplus >= 201402  && (!defined(__EDG_VERSION__) || __EDG_VERSION__ > 411) \
+                           && (!defined(__SUNPRO_CC) || __SUNPRO_CC > 0x5150)
+
+template <class CharT,
+          class = std::enable_if_t<std::is_same<CharT, char>{} ||
+                                   std::is_same<CharT, wchar_t>{} ||
+                                   std::is_same<CharT, char16_t>{} ||
+                                   std::is_same<CharT, char32_t>{}>>
+CONSTCD14
+inline
+string_literal<CharT, 2>
+msl(CharT c) NOEXCEPT
+{
+    return string_literal<CharT, 2>{c};
+}
+
+CONSTCD14
+inline
+std::size_t
+to_string_len(std::intmax_t i)
+{
+    std::size_t r = 0;
+    do
+    {
+        i /= 10;
+        ++r;
+    } while (i > 0);
+    return r;
+}
+
+template <std::intmax_t N>
+CONSTCD14
+inline
+std::enable_if_t
+<
+    N < 10,
+    string_literal<char, to_string_len(N)+1>
+>
+msl() NOEXCEPT
+{
+    return msl(char(N % 10 + '0'));
+}
+
+template <std::intmax_t N>
+CONSTCD14
+inline
+std::enable_if_t
+<
+    10 <= N,
+    string_literal<char, to_string_len(N)+1>
+>
+msl() NOEXCEPT
+{
+    return msl<N/10>() + msl(char(N % 10 + '0'));
+}
+
+template <class CharT, std::intmax_t N, std::intmax_t D>
+CONSTCD14
+inline
+std::enable_if_t
+<
+    std::ratio<N, D>::type::den != 1,
+    string_literal<CharT, to_string_len(std::ratio<N, D>::type::num) +
+                          to_string_len(std::ratio<N, D>::type::den) + 4>
+>
+msl(std::ratio<N, D>) NOEXCEPT
+{
+    using R = typename std::ratio<N, D>::type;
+    return msl(CharT{'['}) + msl<R::num>() + msl(CharT{'/'}) +
+                             msl<R::den>() + msl(CharT{']'});
+}
+
+template <class CharT, std::intmax_t N, std::intmax_t D>
+CONSTCD14
+inline
+std::enable_if_t
+<
+    std::ratio<N, D>::type::den == 1,
+    string_literal<CharT, to_string_len(std::ratio<N, D>::type::num) + 3>
+>
+msl(std::ratio<N, D>) NOEXCEPT
+{
+    using R = typename std::ratio<N, D>::type;
+    return msl(CharT{'['}) + msl<R::num>() + msl(CharT{']'});
+}
+
+
+#else  // __cplusplus < 201402 || (defined(__EDG_VERSION__) && __EDG_VERSION__ <= 411)
+
+inline
+std::string
+to_string(std::uint64_t x)
+{
+    return std::to_string(x);
+}
+
+template <class CharT>
+inline
+std::basic_string<CharT>
+to_string(std::uint64_t x)
+{
+    auto y = std::to_string(x);
+    return std::basic_string<CharT>(y.begin(), y.end());
+}
+
+template <class CharT, std::intmax_t N, std::intmax_t D>
+inline
+typename std::enable_if
+<
+    std::ratio<N, D>::type::den != 1,
+    std::basic_string<CharT>
+>::type
+msl(std::ratio<N, D>)
+{
+    using R = typename std::ratio<N, D>::type;
+    return std::basic_string<CharT>(1, '[') + to_string<CharT>(R::num) + CharT{'/'} +
+                                              to_string<CharT>(R::den) + CharT{']'};
+}
+
+template <class CharT, std::intmax_t N, std::intmax_t D>
+inline
+typename std::enable_if
+<
+    std::ratio<N, D>::type::den == 1,
+    std::basic_string<CharT>
+>::type
+msl(std::ratio<N, D>)
+{
+    using R = typename std::ratio<N, D>::type;
+    return std::basic_string<CharT>(1, '[') + to_string<CharT>(R::num) + CharT{']'};
+}
+
+#endif  // __cplusplus < 201402 || (defined(__EDG_VERSION__) && __EDG_VERSION__ <= 411)
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::atto) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'a'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::femto) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'f'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::pico) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'p'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::nano) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'n'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+typename std::enable_if
+<
+    std::is_same<CharT, char>::value,
+    string_literal<char, 3>
+>::type
+msl(std::micro) NOEXCEPT
+{
+    return string_literal<char, 3>{'\xC2', '\xB5'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+typename std::enable_if
+<
+    !std::is_same<CharT, char>::value,
+    string_literal<CharT, 2>
+>::type
+msl(std::micro) NOEXCEPT
+{
+    return string_literal<CharT, 2>{CharT{static_cast<unsigned char>('\xB5')}};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::milli) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'m'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::centi) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'c'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 3>
+msl(std::deca) NOEXCEPT
+{
+    return string_literal<CharT, 3>{'d', 'a'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::deci) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'d'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::hecto) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'h'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::kilo) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'k'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::mega) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'M'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::giga) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'G'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::tera) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'T'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::peta) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'P'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+msl(std::exa) NOEXCEPT
+{
+    return string_literal<CharT, 2>{'E'};
+}
+
+template <class CharT, class Period>
+CONSTCD11
+inline
+auto
+get_units(Period p)
+ -> decltype(msl<CharT>(p) + string_literal<CharT, 2>{'s'})
+{
+    return msl<CharT>(p) + string_literal<CharT, 2>{'s'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+get_units(std::ratio<1>)
+{
+    return string_literal<CharT, 2>{'s'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+get_units(std::ratio<3600>)
+{
+    return string_literal<CharT, 2>{'h'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 4>
+get_units(std::ratio<60>)
+{
+    return string_literal<CharT, 4>{'m', 'i', 'n'};
+}
+
+template <class CharT>
+CONSTCD11
+inline
+string_literal<CharT, 2>
+get_units(std::ratio<86400>)
+{
+    return string_literal<CharT, 2>{'d'};
+}
+
+template <class CharT, class Traits = std::char_traits<CharT>>
+struct make_string;
+
+template <>
+struct make_string<char>
+{
+    template <class Rep>
+    static
+    std::string
+    from(Rep n)
+    {
+        return std::to_string(n);
+    }
+};
+
+template <class Traits>
+struct make_string<char, Traits>
+{
+    template <class Rep>
+    static
+    std::basic_string<char, Traits>
+    from(Rep n)
+    {
+        auto s = std::to_string(n);
+        return std::basic_string<char, Traits>(s.begin(), s.end());
+    }
+};
+
+template <>
+struct make_string<wchar_t>
+{
+    template <class Rep>
+    static
+    std::wstring
+    from(Rep n)
+    {
+        return std::to_wstring(n);
+    }
+};
+
+template <class Traits>
+struct make_string<wchar_t, Traits>
+{
+    template <class Rep>
+    static
+    std::basic_string<wchar_t, Traits>
+    from(Rep n)
+    {
+        auto s = std::to_wstring(n);
+        return std::basic_string<wchar_t, Traits>(s.begin(), s.end());
+    }
+};
+
+}  // namespace detail
+
+// to_stream
+
+CONSTDATA year nanyear{-32768};
+
+template <class Duration>
+struct fields
+{
+    year_month_day        ymd{nanyear/0/0};
+    weekday               wd{8u};
+    hh_mm_ss<Duration>    tod{};
+    bool                  has_tod = false;
+
+    fields() = default;
+
+    fields(year_month_day ymd_) : ymd(ymd_) {}
+    fields(weekday wd_) : wd(wd_) {}
+    fields(hh_mm_ss<Duration> tod_) : tod(tod_), has_tod(true) {}
+
+    fields(year_month_day ymd_, weekday wd_) : ymd(ymd_), wd(wd_) {}
+    fields(year_month_day ymd_, hh_mm_ss<Duration> tod_) : ymd(ymd_), tod(tod_),
+                                                           has_tod(true) {}
+
+    fields(weekday wd_, hh_mm_ss<Duration> tod_) : wd(wd_), tod(tod_), has_tod(true) {}
+
+    fields(year_month_day ymd_, weekday wd_, hh_mm_ss<Duration> tod_)
+        : ymd(ymd_)
+        , wd(wd_)
+        , tod(tod_)
+        , has_tod(true)
+        {}
+};
+
+namespace detail
+{
+
+template <class CharT, class Traits, class Duration>
+unsigned
+extract_weekday(std::basic_ostream<CharT, Traits>& os, const fields<Duration>& fds)
+{
+    if (!fds.ymd.ok() && !fds.wd.ok())
+    {
+        // fds does not contain a valid weekday
+        os.setstate(std::ios::failbit);
+        return 8;
+    }
+    weekday wd;
+    if (fds.ymd.ok())
+    {
+        wd = weekday{sys_days(fds.ymd)};
+        if (fds.wd.ok() && wd != fds.wd)
+        {
+            // fds.ymd and fds.wd are inconsistent
+            os.setstate(std::ios::failbit);
+            return 8;
+        }
+    }
+    else
+        wd = fds.wd;
+    return static_cast<unsigned>((wd - Sunday).count());
+}
+
+template <class CharT, class Traits, class Duration>
+unsigned
+extract_month(std::basic_ostream<CharT, Traits>& os, const fields<Duration>& fds)
+{
+    if (!fds.ymd.month().ok())
+    {
+        // fds does not contain a valid month
+        os.setstate(std::ios::failbit);
+        return 0;
+    }
+    return static_cast<unsigned>(fds.ymd.month());
+}
+
+}  // namespace detail
+
+#if ONLY_C_LOCALE
+
+namespace detail
+{
+
+inline
+std::pair<const std::string*, const std::string*>
+weekday_names()
+{
+    static const std::string nm[] =
+    {
+        "Sunday",
+        "Monday",
+        "Tuesday",
+        "Wednesday",
+        "Thursday",
+        "Friday",
+        "Saturday",
+        "Sun",
+        "Mon",
+        "Tue",
+        "Wed",
+        "Thu",
+        "Fri",
+        "Sat"
+    };
+    return std::make_pair(nm, nm+sizeof(nm)/sizeof(nm[0]));
+}
+
+inline
+std::pair<const std::string*, const std::string*>
+month_names()
+{
+    static const std::string nm[] =
+    {
+        "January",
+        "February",
+        "March",
+        "April",
+        "May",
+        "June",
+        "July",
+        "August",
+        "September",
+        "October",
+        "November",
+        "December",
+        "Jan",
+        "Feb",
+        "Mar",
+        "Apr",
+        "May",
+        "Jun",
+        "Jul",
+        "Aug",
+        "Sep",
+        "Oct",
+        "Nov",
+        "Dec"
+    };
+    return std::make_pair(nm, nm+sizeof(nm)/sizeof(nm[0]));
+}
+
+inline
+std::pair<const std::string*, const std::string*>
+ampm_names()
+{
+    static const std::string nm[] =
+    {
+        "AM",
+        "PM"
+    };
+    return std::make_pair(nm, nm+sizeof(nm)/sizeof(nm[0]));
+}
+
+template <class CharT, class Traits, class FwdIter>
+FwdIter
+scan_keyword(std::basic_istream<CharT, Traits>& is, FwdIter kb, FwdIter ke)
+{
+    size_t nkw = static_cast<size_t>(std::distance(kb, ke));
+    const unsigned char doesnt_match = '\0';
+    const unsigned char might_match = '\1';
+    const unsigned char does_match = '\2';
+    unsigned char statbuf[100];
+    unsigned char* status = statbuf;
+    std::unique_ptr<unsigned char, void(*)(void*)> stat_hold(0, free);
+    if (nkw > sizeof(statbuf))
+    {
+        status = (unsigned char*)std::malloc(nkw);
+        if (status == nullptr)
+            throw std::bad_alloc();
+        stat_hold.reset(status);
+    }
+    size_t n_might_match = nkw;  // At this point, any keyword might match
+    size_t n_does_match = 0;     // but none of them definitely do
+    // Initialize all statuses to might_match, except for "" keywords are does_match
+    unsigned char* st = status;
+    for (auto ky = kb; ky != ke; ++ky, ++st)
+    {
+        if (!ky->empty())
+            *st = might_match;
+        else
+        {
+            *st = does_match;
+            --n_might_match;
+            ++n_does_match;
+        }
+    }
+    // While there might be a match, test keywords against the next CharT
+    for (size_t indx = 0; is && n_might_match > 0; ++indx)
+    {
+        // Peek at the next CharT but don't consume it
+        auto ic = is.peek();
+        if (ic == EOF)
+        {
+            is.setstate(std::ios::eofbit);
+            break;
+        }
+        auto c = static_cast<char>(toupper(ic));
+        bool consume = false;
+        // For each keyword which might match, see if the indx character is c
+        // If a match if found, consume c
+        // If a match is found, and that is the last character in the keyword,
+        //    then that keyword matches.
+        // If the keyword doesn't match this character, then change the keyword
+        //    to doesn't match
+        st = status;
+        for (auto ky = kb; ky != ke; ++ky, ++st)
+        {
+            if (*st == might_match)
+            {
+                if (c == static_cast<char>(toupper((*ky)[indx])))
+                {
+                    consume = true;
+                    if (ky->size() == indx+1)
+                    {
+                        *st = does_match;
+                        --n_might_match;
+                        ++n_does_match;
+                    }
+                }
+                else
+                {
+                    *st = doesnt_match;
+                    --n_might_match;
+                }
+            }
+        }
+        // consume if we matched a character
+        if (consume)
+        {
+            (void)is.get();
+            // If we consumed a character and there might be a matched keyword that
+            //   was marked matched on a previous iteration, then such keywords
+            //   are now marked as not matching.
+            if (n_might_match + n_does_match > 1)
+            {
+                st = status;
+                for (auto ky = kb; ky != ke; ++ky, ++st)
+                {
+                    if (*st == does_match && ky->size() != indx+1)
+                    {
+                        *st = doesnt_match;
+                        --n_does_match;
+                    }
+                }
+            }
+        }
+    }
+    // We've exited the loop because we hit eof and/or we have no more "might matches".
+    // Return the first matching result
+    for (st = status; kb != ke; ++kb, ++st)
+        if (*st == does_match)
+            break;
+    if (kb == ke)
+        is.setstate(std::ios::failbit);
+    return kb;
+}
+
+}  // namespace detail
+
+#endif  // ONLY_C_LOCALE
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const fields<Duration>& fds, const std::string* abbrev,
+          const std::chrono::seconds* offset_sec)
+{
+#if ONLY_C_LOCALE
+    using detail::weekday_names;
+    using detail::month_names;
+    using detail::ampm_names;
+#endif
+    using detail::save_ostream;
+    using detail::get_units;
+    using detail::extract_weekday;
+    using detail::extract_month;
+    using std::ios;
+    using std::chrono::duration_cast;
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    using std::chrono::hours;
+    date::detail::save_ostream<CharT, Traits> ss(os);
+    os.fill(' ');
+    os.flags(std::ios::skipws | std::ios::dec);
+    os.width(0);
+    tm tm{};
+    bool insert_negative = fds.has_tod && fds.tod.to_duration() < Duration::zero();
+#if !ONLY_C_LOCALE
+    auto& facet = std::use_facet<std::time_put<CharT>>(os.getloc());
+#endif
+    const CharT* command = nullptr;
+    CharT modified = CharT{};
+    for (; *fmt; ++fmt)
+    {
+        switch (*fmt)
+        {
+        case 'a':
+        case 'A':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
+                    if (os.fail())
+                        return os;
+#if !ONLY_C_LOCALE
+                    const CharT f[] = {'%', *fmt};
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+#else  // ONLY_C_LOCALE
+                    os << weekday_names().first[tm.tm_wday+7*(*fmt == 'a')];
+#endif  // ONLY_C_LOCALE
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'b':
+        case 'B':
+        case 'h':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    tm.tm_mon = static_cast<int>(extract_month(os, fds)) - 1;
+#if !ONLY_C_LOCALE
+                    const CharT f[] = {'%', *fmt};
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+#else  // ONLY_C_LOCALE
+                    os << month_names().first[tm.tm_mon+12*(*fmt != 'B')];
+#endif  // ONLY_C_LOCALE
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'c':
+        case 'x':
+            if (command)
+            {
+                if (modified == CharT{'O'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    if (*fmt == 'c' && !fds.has_tod)
+                        os.setstate(std::ios::failbit);
+#if !ONLY_C_LOCALE
+                    tm = std::tm{};
+                    auto const& ymd = fds.ymd;
+                    auto ld = local_days(ymd);
+                    if (*fmt == 'c')
+                    {
+                        tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
+                        tm.tm_min = static_cast<int>(fds.tod.minutes().count());
+                        tm.tm_hour = static_cast<int>(fds.tod.hours().count());
+                    }
+                    tm.tm_mday = static_cast<int>(static_cast<unsigned>(ymd.day()));
+                    tm.tm_mon = static_cast<int>(extract_month(os, fds) - 1);
+                    tm.tm_year = static_cast<int>(ymd.year()) - 1900;
+                    tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
+                    if (os.fail())
+                        return os;
+                    tm.tm_yday = static_cast<int>((ld - local_days(ymd.year()/1/1)).count());
+                    CharT f[3] = {'%'};
+                    auto fe = std::begin(f) + 1;
+                    if (modified == CharT{'E'})
+                        *fe++ = modified;
+                    *fe++ = *fmt;
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), fe);
+#else  // ONLY_C_LOCALE
+                    if (*fmt == 'c')
+                    {
+                        auto wd = static_cast<int>(extract_weekday(os, fds));
+                        os << weekday_names().first[static_cast<unsigned>(wd)+7]
+                           << ' ';
+                        os << month_names().first[extract_month(os, fds)-1+12] << ' ';
+                        auto d = static_cast<int>(static_cast<unsigned>(fds.ymd.day()));
+                        if (d < 10)
+                            os << ' ';
+                        os << d << ' '
+                           << make_time(duration_cast<seconds>(fds.tod.to_duration()))
+                           << ' ' << fds.ymd.year();
+
+                    }
+                    else  // *fmt == 'x'
+                    {
+                        auto const& ymd = fds.ymd;
+                        save_ostream<CharT, Traits> _(os);
+                        os.fill('0');
+                        os.flags(std::ios::dec | std::ios::right);
+                        os.width(2);
+                        os << static_cast<unsigned>(ymd.month()) << CharT{'/'};
+                        os.width(2);
+                        os << static_cast<unsigned>(ymd.day()) << CharT{'/'};
+                        os.width(2);
+                        os << static_cast<int>(ymd.year()) % 100;
+                    }
+#endif  // ONLY_C_LOCALE
+                }
+                command = nullptr;
+                modified = CharT{};
+            }
+            else
+                os << *fmt;
+            break;
+        case 'C':
+            if (command)
+            {
+                if (modified == CharT{'O'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.year().ok())
+                        os.setstate(std::ios::failbit);
+                    auto y = static_cast<int>(fds.ymd.year());
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        save_ostream<CharT, Traits> _(os);
+                        os.fill('0');
+                        os.flags(std::ios::dec | std::ios::right);
+                        if (y >= 0)
+                        {
+                            os.width(2);
+                            os << y/100;
+                        }
+                        else
+                        {
+                            os << CharT{'-'};
+                            os.width(2);
+                            os << -(y-99)/100;
+                        }
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'E'})
+                    {
+                        tm.tm_year = y - 1900;
+                        CharT f[3] = {'%', 'E', 'C'};
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                command = nullptr;
+                modified = CharT{};
+            }
+            else
+                os << *fmt;
+            break;
+        case 'd':
+        case 'e':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.day().ok())
+                        os.setstate(std::ios::failbit);
+                    auto d = static_cast<int>(static_cast<unsigned>(fds.ymd.day()));
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        save_ostream<CharT, Traits> _(os);
+                        if (*fmt == CharT{'d'})
+                            os.fill('0');
+                        else
+                            os.fill(' ');
+                        os.flags(std::ios::dec | std::ios::right);
+                        os.width(2);
+                        os << d;
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        tm.tm_mday = d;
+                        CharT f[3] = {'%', 'O', *fmt};
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                command = nullptr;
+                modified = CharT{};
+            }
+            else
+                os << *fmt;
+            break;
+        case 'D':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    auto const& ymd = fds.ymd;
+                    save_ostream<CharT, Traits> _(os);
+                    os.fill('0');
+                    os.flags(std::ios::dec | std::ios::right);
+                    os.width(2);
+                    os << static_cast<unsigned>(ymd.month()) << CharT{'/'};
+                    os.width(2);
+                    os << static_cast<unsigned>(ymd.day()) << CharT{'/'};
+                    os.width(2);
+                    os << static_cast<int>(ymd.year()) % 100;
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'F':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    auto const& ymd = fds.ymd;
+                    save_ostream<CharT, Traits> _(os);
+                    os.imbue(std::locale::classic());
+                    os.fill('0');
+                    os.flags(std::ios::dec | std::ios::right);
+                    os.width(4);
+                    os << static_cast<int>(ymd.year()) << CharT{'-'};
+                    os.width(2);
+                    os << static_cast<unsigned>(ymd.month()) << CharT{'-'};
+                    os.width(2);
+                    os << static_cast<unsigned>(ymd.day());
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'g':
+        case 'G':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    auto ld = local_days(fds.ymd);
+                    auto y = year_month_day{ld + days{3}}.year();
+                    auto start = local_days((y-years{1})/December/Thursday[last]) +
+                                 (Monday-Thursday);
+                    if (ld < start)
+                        --y;
+                    if (*fmt == CharT{'G'})
+                        os << y;
+                    else
+                    {
+                        save_ostream<CharT, Traits> _(os);
+                        os.fill('0');
+                        os.flags(std::ios::dec | std::ios::right);
+                        os.width(2);
+                        os << std::abs(static_cast<int>(y)) % 100;
+                    }
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'H':
+        case 'I':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+                    if (insert_negative)
+                    {
+                        os << '-';
+                        insert_negative = false;
+                    }
+                    auto hms = fds.tod;
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        auto h = *fmt == CharT{'I'} ? date::make12(hms.hours()) : hms.hours();
+                        if (h < hours{10})
+                            os << CharT{'0'};
+                        os << h.count();
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_hour = static_cast<int>(hms.hours().count());
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'j':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (fds.ymd.ok() || fds.has_tod)
+                    {
+                        days doy;
+                        if (fds.ymd.ok())
+                        {
+                            auto ld = local_days(fds.ymd);
+                            auto y = fds.ymd.year();
+                            doy = ld - local_days(y/January/1) + days{1};
+                        }
+                        else
+                        {
+                            doy = duration_cast<days>(fds.tod.to_duration());
+                        }
+                        save_ostream<CharT, Traits> _(os);
+                        os.fill('0');
+                        os.flags(std::ios::dec | std::ios::right);
+                        os.width(3);
+                        os << doy.count();
+                    }
+                    else
+                    {
+                        os.setstate(std::ios::failbit);
+                    }
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'm':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.month().ok())
+                        os.setstate(std::ios::failbit);
+                    auto m = static_cast<unsigned>(fds.ymd.month());
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        if (m < 10)
+                            os << CharT{'0'};
+                        os << m;
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_mon = static_cast<int>(m-1);
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'M':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+                    if (insert_negative)
+                    {
+                        os << '-';
+                        insert_negative = false;
+                    }
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        if (fds.tod.minutes() < minutes{10})
+                            os << CharT{'0'};
+                        os << fds.tod.minutes().count();
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_min = static_cast<int>(fds.tod.minutes().count());
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'n':
+            if (command)
+            {
+                if (modified == CharT{})
+                    os << CharT{'\n'};
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'p':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+#if !ONLY_C_LOCALE
+                    const CharT f[] = {'%', *fmt};
+                    tm.tm_hour = static_cast<int>(fds.tod.hours().count());
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+#else
+                    if (date::is_am(fds.tod.hours()))
+                        os << ampm_names().first[0];
+                    else
+                        os << ampm_names().first[1];
+#endif
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'Q':
+        case 'q':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+                    auto d = fds.tod.to_duration();
+                    if (*fmt == 'q')
+                        os << get_units<CharT>(typename decltype(d)::period::type{});
+                    else
+                        os << d.count();
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'r':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+#if !ONLY_C_LOCALE
+                    const CharT f[] = {'%', *fmt};
+                    tm.tm_hour = static_cast<int>(fds.tod.hours().count());
+                    tm.tm_min = static_cast<int>(fds.tod.minutes().count());
+                    tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+#else
+                    hh_mm_ss<seconds> tod(duration_cast<seconds>(fds.tod.to_duration()));
+                    save_ostream<CharT, Traits> _(os);
+                    os.fill('0');
+                    os.width(2);
+                    os << date::make12(tod.hours()).count() << CharT{':'};
+                    os.width(2);
+                    os << tod.minutes().count() << CharT{':'};
+                    os.width(2);
+                    os << tod.seconds().count() << CharT{' '};
+                    if (date::is_am(tod.hours()))
+                        os << ampm_names().first[0];
+                    else
+                        os << ampm_names().first[1];
+#endif
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'R':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+                    if (fds.tod.hours() < hours{10})
+                        os << CharT{'0'};
+                    os << fds.tod.hours().count() << CharT{':'};
+                    if (fds.tod.minutes() < minutes{10})
+                        os << CharT{'0'};
+                    os << fds.tod.minutes().count();
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'S':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+                    if (insert_negative)
+                    {
+                        os << '-';
+                        insert_negative = false;
+                    }
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        os << fds.tod.s_;
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_sec = static_cast<int>(fds.tod.s_.seconds().count());
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 't':
+            if (command)
+            {
+                if (modified == CharT{})
+                    os << CharT{'\t'};
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'T':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+                    os << fds.tod;
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'u':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    auto wd = extract_weekday(os, fds);
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        os << (wd != 0 ? wd : 7u);
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_wday = static_cast<int>(wd);
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'U':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    auto const& ymd = fds.ymd;
+                    if (!ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    auto ld = local_days(ymd);
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        auto st = local_days(Sunday[1]/January/ymd.year());
+                        if (ld < st)
+                            os << CharT{'0'} << CharT{'0'};
+                        else
+                        {
+                            auto wn = duration_cast<weeks>(ld - st).count() + 1;
+                            if (wn < 10)
+                                os << CharT{'0'};
+                            os << wn;
+                        }
+                   }
+ #if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_year = static_cast<int>(ymd.year()) - 1900;
+                        tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
+                        if (os.fail())
+                            return os;
+                        tm.tm_yday = static_cast<int>((ld - local_days(ymd.year()/1/1)).count());
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'V':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    auto ld = local_days(fds.ymd);
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        auto y = year_month_day{ld + days{3}}.year();
+                        auto st = local_days((y-years{1})/12/Thursday[last]) +
+                                  (Monday-Thursday);
+                        if (ld < st)
+                        {
+                            --y;
+                            st = local_days((y - years{1})/12/Thursday[last]) +
+                                 (Monday-Thursday);
+                        }
+                        auto wn = duration_cast<weeks>(ld - st).count() + 1;
+                        if (wn < 10)
+                            os << CharT{'0'};
+                        os << wn;
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        auto const& ymd = fds.ymd;
+                        tm.tm_year = static_cast<int>(ymd.year()) - 1900;
+                        tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
+                        if (os.fail())
+                            return os;
+                        tm.tm_yday = static_cast<int>((ld - local_days(ymd.year()/1/1)).count());
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'w':
+            if (command)
+            {
+                auto wd = extract_weekday(os, fds);
+                if (os.fail())
+                    return os;
+#if !ONLY_C_LOCALE
+                if (modified == CharT{})
+#else
+                if (modified != CharT{'E'})
+#endif
+                {
+                    os << wd;
+                }
+#if !ONLY_C_LOCALE
+                else if (modified == CharT{'O'})
+                {
+                    const CharT f[] = {'%', modified, *fmt};
+                    tm.tm_wday = static_cast<int>(wd);
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                }
+#endif
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'W':
+            if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    auto const& ymd = fds.ymd;
+                    if (!ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    auto ld = local_days(ymd);
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        auto st = local_days(Monday[1]/January/ymd.year());
+                        if (ld < st)
+                            os << CharT{'0'} << CharT{'0'};
+                        else
+                        {
+                            auto wn = duration_cast<weeks>(ld - st).count() + 1;
+                            if (wn < 10)
+                                os << CharT{'0'};
+                            os << wn;
+                        }
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_year = static_cast<int>(ymd.year()) - 1900;
+                        tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
+                        if (os.fail())
+                            return os;
+                        tm.tm_yday = static_cast<int>((ld - local_days(ymd.year()/1/1)).count());
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'X':
+            if (command)
+            {
+                if (modified == CharT{'O'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
+#if !ONLY_C_LOCALE
+                    tm = std::tm{};
+                    tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
+                    tm.tm_min = static_cast<int>(fds.tod.minutes().count());
+                    tm.tm_hour = static_cast<int>(fds.tod.hours().count());
+                    CharT f[3] = {'%'};
+                    auto fe = std::begin(f) + 1;
+                    if (modified == CharT{'E'})
+                        *fe++ = modified;
+                    *fe++ = *fmt;
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), fe);
+#else
+                    os << fds.tod;
+#endif
+                }
+                command = nullptr;
+                modified = CharT{};
+            }
+            else
+                os << *fmt;
+            break;
+        case 'y':
+            if (command)
+            {
+                if (!fds.ymd.year().ok())
+                    os.setstate(std::ios::failbit);
+                auto y = static_cast<int>(fds.ymd.year());
+#if !ONLY_C_LOCALE
+                if (modified == CharT{})
+                {
+#endif
+                    y = std::abs(y) % 100;
+                    if (y < 10)
+                        os << CharT{'0'};
+                    os << y;
+#if !ONLY_C_LOCALE
+                }
+                else
+                {
+                    const CharT f[] = {'%', modified, *fmt};
+                    tm.tm_year = y - 1900;
+                    facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                }
+#endif
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'Y':
+            if (command)
+            {
+                if (modified == CharT{'O'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.year().ok())
+                        os.setstate(std::ios::failbit);
+                    auto y = fds.ymd.year();
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        save_ostream<CharT, Traits> _(os);
+                        os.imbue(std::locale::classic());
+                        os << y;
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'E'})
+                    {
+                        const CharT f[] = {'%', modified, *fmt};
+                        tm.tm_year = static_cast<int>(y) - 1900;
+                        facet.put(os, os, os.fill(), &tm, std::begin(f), std::end(f));
+                    }
+#endif
+                }
+                modified = CharT{};
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'z':
+            if (command)
+            {
+                if (offset_sec == nullptr)
+                {
+                    // Can not format %z with unknown offset
+                    os.setstate(ios::failbit);
+                    return os;
+                }
+                auto m = duration_cast<minutes>(*offset_sec);
+                auto neg = m < minutes{0};
+                m = date::abs(m);
+                auto h = duration_cast<hours>(m);
+                m -= h;
+                if (neg)
+                    os << CharT{'-'};
+                else
+                    os << CharT{'+'};
+                if (h < hours{10})
+                    os << CharT{'0'};
+                os << h.count();
+                if (modified != CharT{})
+                    os << CharT{':'};
+                if (m < minutes{10})
+                    os << CharT{'0'};
+                os << m.count();
+                command = nullptr;
+                modified = CharT{};
+            }
+            else
+                os << *fmt;
+            break;
+        case 'Z':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    if (abbrev == nullptr)
+                    {
+                        // Can not format %Z with unknown time_zone
+                        os.setstate(ios::failbit);
+                        return os;
+                    }
+                    for (auto c : *abbrev)
+                        os << CharT(c);
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    modified = CharT{};
+                }
+                command = nullptr;
+            }
+            else
+                os << *fmt;
+            break;
+        case 'E':
+        case 'O':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    modified = *fmt;
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << *fmt;
+                    command = nullptr;
+                    modified = CharT{};
+                }
+            }
+            else
+                os << *fmt;
+            break;
+        case '%':
+            if (command)
+            {
+                if (modified == CharT{})
+                {
+                    os << CharT{'%'};
+                    command = nullptr;
+                }
+                else
+                {
+                    os << CharT{'%'} << modified << CharT{'%'};
+                    command = nullptr;
+                    modified = CharT{};
+                }
+            }
+            else
+                command = fmt;
+            break;
+        default:
+            if (command)
+            {
+                os << CharT{'%'};
+                command = nullptr;
+            }
+            if (modified != CharT{})
+            {
+                os << modified;
+                modified = CharT{};
+            }
+            os << *fmt;
+            break;
+        }
+    }
+    if (command)
+        os << CharT{'%'};
+    if (modified != CharT{})
+        os << modified;
+    return os;
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const year& y)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{y/0/0};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const month& m)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{m/0/nanyear};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const day& d)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{d/0/nanyear};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const weekday& wd)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{wd};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const year_month& ym)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{ym/0};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const month_day& md)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{md/nanyear};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const year_month_day& ymd)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{ymd};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits, class Rep, class Period>
+inline
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const std::chrono::duration<Rep, Period>& d)
+{
+    using Duration = std::chrono::duration<Rep, Period>;
+    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
+    fields<CT> fds{hh_mm_ss<CT>{d}};
+    return to_stream(os, fmt, fds);
+}
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const local_time<Duration>& tp, const std::string* abbrev = nullptr,
+          const std::chrono::seconds* offset_sec = nullptr)
+{
+    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
+    auto ld = floor<days>(tp);
+    fields<CT> fds{year_month_day{ld}, hh_mm_ss<CT>{tp-local_seconds{ld}}};
+    return to_stream(os, fmt, fds, abbrev, offset_sec);
+}
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const sys_time<Duration>& tp)
+{
+    using std::chrono::seconds;
+    using CT = typename std::common_type<Duration, seconds>::type;
+    const std::string abbrev("UTC");
+    CONSTDATA seconds offset{0};
+    auto sd = floor<days>(tp);
+    fields<CT> fds{year_month_day{sd}, hh_mm_ss<CT>{tp-sys_seconds{sd}}};
+    return to_stream(os, fmt, fds, &abbrev, &offset);
+}
+
+// format
+
+template <class CharT, class Streamable>
+auto
+format(const std::locale& loc, const CharT* fmt, const Streamable& tp)
+    -> decltype(to_stream(std::declval<std::basic_ostream<CharT>&>(), fmt, tp),
+                std::basic_string<CharT>{})
+{
+    std::basic_ostringstream<CharT> os;
+    os.exceptions(std::ios::failbit | std::ios::badbit);
+    os.imbue(loc);
+    to_stream(os, fmt, tp);
+    return os.str();
+}
+
+template <class CharT, class Streamable>
+auto
+format(const CharT* fmt, const Streamable& tp)
+    -> decltype(to_stream(std::declval<std::basic_ostream<CharT>&>(), fmt, tp),
+                std::basic_string<CharT>{})
+{
+    std::basic_ostringstream<CharT> os;
+    os.exceptions(std::ios::failbit | std::ios::badbit);
+    to_stream(os, fmt, tp);
+    return os.str();
+}
+
+template <class CharT, class Traits, class Alloc, class Streamable>
+auto
+format(const std::locale& loc, const std::basic_string<CharT, Traits, Alloc>& fmt,
+       const Streamable& tp)
+    -> decltype(to_stream(std::declval<std::basic_ostream<CharT, Traits>&>(), fmt.c_str(), tp),
+                std::basic_string<CharT, Traits, Alloc>{})
+{
+    std::basic_ostringstream<CharT, Traits, Alloc> os;
+    os.exceptions(std::ios::failbit | std::ios::badbit);
+    os.imbue(loc);
+    to_stream(os, fmt.c_str(), tp);
+    return os.str();
+}
+
+template <class CharT, class Traits, class Alloc, class Streamable>
+auto
+format(const std::basic_string<CharT, Traits, Alloc>& fmt, const Streamable& tp)
+    -> decltype(to_stream(std::declval<std::basic_ostream<CharT, Traits>&>(), fmt.c_str(), tp),
+                std::basic_string<CharT, Traits, Alloc>{})
+{
+    std::basic_ostringstream<CharT, Traits, Alloc> os;
+    os.exceptions(std::ios::failbit | std::ios::badbit);
+    to_stream(os, fmt.c_str(), tp);
+    return os.str();
+}
+
+// parse
+
+namespace detail
+{
+
+template <class CharT, class Traits>
+bool
+read_char(std::basic_istream<CharT, Traits>& is, CharT fmt, std::ios::iostate& err)
+{
+    auto ic = is.get();
+    if (Traits::eq_int_type(ic, Traits::eof()) ||
+       !Traits::eq(Traits::to_char_type(ic), fmt))
+    {
+        err |= std::ios::failbit;
+        is.setstate(std::ios::failbit);
+        return false;
+    }
+    return true;
+}
+
+template <class CharT, class Traits>
+unsigned
+read_unsigned(std::basic_istream<CharT, Traits>& is, unsigned m = 1, unsigned M = 10)
+{
+    unsigned x = 0;
+    unsigned count = 0;
+    while (true)
+    {
+        auto ic = is.peek();
+        if (Traits::eq_int_type(ic, Traits::eof()))
+            break;
+        auto c = static_cast<char>(Traits::to_char_type(ic));
+        if (!('0' <= c && c <= '9'))
+            break;
+        (void)is.get();
+        ++count;
+        x = 10*x + static_cast<unsigned>(c - '0');
+        if (count == M)
+            break;
+    }
+    if (count < m)
+        is.setstate(std::ios::failbit);
+    return x;
+}
+
+template <class CharT, class Traits>
+int
+read_signed(std::basic_istream<CharT, Traits>& is, unsigned m = 1, unsigned M = 10)
+{
+    auto ic = is.peek();
+    if (!Traits::eq_int_type(ic, Traits::eof()))
+    {
+        auto c = static_cast<char>(Traits::to_char_type(ic));
+        if (('0' <= c && c <= '9') || c == '-' || c == '+')
+        {
+            if (c == '-' || c == '+')
+                (void)is.get();
+            auto x = static_cast<int>(read_unsigned(is, std::max(m, 1u), M));
+            if (!is.fail())
+            {
+                if (c == '-')
+                    x = -x;
+                return x;
+            }
+        }
+    }
+    if (m > 0)
+        is.setstate(std::ios::failbit);
+    return 0;
+}
+
+template <class CharT, class Traits>
+long double
+read_long_double(std::basic_istream<CharT, Traits>& is, unsigned m = 1, unsigned M = 10)
+{
+    unsigned count = 0;
+    auto decimal_point = Traits::to_int_type(
+        std::use_facet<std::numpunct<CharT>>(is.getloc()).decimal_point());
+    std::string buf;
+    while (true)
+    {
+        auto ic = is.peek();
+        if (Traits::eq_int_type(ic, Traits::eof()))
+            break;
+        if (Traits::eq_int_type(ic, decimal_point))
+        {
+            buf += '.';
+            decimal_point = Traits::eof();
+            is.get();
+        }
+        else
+        {
+            auto c = static_cast<char>(Traits::to_char_type(ic));
+            if (!('0' <= c && c <= '9'))
+                break;
+            buf += c;
+            (void)is.get();
+        }
+        if (++count == M)
+            break;
+    }
+    if (count < m)
+    {
+        is.setstate(std::ios::failbit);
+        return 0;
+    }
+    return std::stold(buf);
+}
+
+struct rs
+{
+    int& i;
+    unsigned m;
+    unsigned M;
+};
+
+struct ru
+{
+    int& i;
+    unsigned m;
+    unsigned M;
+};
+
+struct rld
+{
+    long double& i;
+    unsigned m;
+    unsigned M;
+};
+
+template <class CharT, class Traits>
+void
+read(std::basic_istream<CharT, Traits>&)
+{
+}
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, CharT a0, Args&& ...args);
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, rs a0, Args&& ...args);
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, ru a0, Args&& ...args);
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, int a0, Args&& ...args);
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, rld a0, Args&& ...args);
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, CharT a0, Args&& ...args)
+{
+    // No-op if a0 == CharT{}
+    if (a0 != CharT{})
+    {
+        auto ic = is.peek();
+        if (Traits::eq_int_type(ic, Traits::eof()))
+        {
+            is.setstate(std::ios::failbit | std::ios::eofbit);
+            return;
+        }
+        if (!Traits::eq(Traits::to_char_type(ic), a0))
+        {
+            is.setstate(std::ios::failbit);
+            return;
+        }
+        (void)is.get();
+    }
+    read(is, std::forward<Args>(args)...);
+}
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, rs a0, Args&& ...args)
+{
+    auto x = read_signed(is, a0.m, a0.M);
+    if (is.fail())
+        return;
+    a0.i = x;
+    read(is, std::forward<Args>(args)...);
+}
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, ru a0, Args&& ...args)
+{
+    auto x = read_unsigned(is, a0.m, a0.M);
+    if (is.fail())
+        return;
+    a0.i = static_cast<int>(x);
+    read(is, std::forward<Args>(args)...);
+}
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, int a0, Args&& ...args)
+{
+    if (a0 != -1)
+    {
+        auto u = static_cast<unsigned>(a0);
+        CharT buf[std::numeric_limits<unsigned>::digits10+2u] = {};
+        auto e = buf;
+        do
+        {
+            *e++ = static_cast<CharT>(CharT(u % 10) + CharT{'0'});
+            u /= 10;
+        } while (u > 0);
+        std::reverse(buf, e);
+        for (auto p = buf; p != e && is.rdstate() == std::ios::goodbit; ++p)
+            read(is, *p);
+    }
+    if (is.rdstate() == std::ios::goodbit)
+        read(is, std::forward<Args>(args)...);
+}
+
+template <class CharT, class Traits, class ...Args>
+void
+read(std::basic_istream<CharT, Traits>& is, rld a0, Args&& ...args)
+{
+    auto x = read_long_double(is, a0.m, a0.M);
+    if (is.fail())
+        return;
+    a0.i = x;
+    read(is, std::forward<Args>(args)...);
+}
+
+template <class T, class CharT, class Traits>
+inline
+void
+checked_set(T& value, T from, T not_a_value, std::basic_ios<CharT, Traits>& is)
+{
+    if (!is.fail())
+    {
+        if (value == not_a_value)
+            value = std::move(from);
+        else if (value != from)
+            is.setstate(std::ios::failbit);
+    }
+}
+
+}  // namespace detail;
+
+template <class CharT, class Traits, class Duration, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            fields<Duration>& fds, std::basic_string<CharT, Traits, Alloc>* abbrev,
+            std::chrono::minutes* offset)
+{
+    using std::numeric_limits;
+    using std::ios;
+    using std::chrono::duration;
+    using std::chrono::duration_cast;
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    using std::chrono::hours;
+    typename std::basic_istream<CharT, Traits>::sentry ok{is, true};
+    if (ok)
+    {
+        date::detail::save_istream<CharT, Traits> ss(is);
+        is.fill(' ');
+        is.flags(std::ios::skipws | std::ios::dec);
+        is.width(0);
+#if !ONLY_C_LOCALE
+        auto& f = std::use_facet<std::time_get<CharT>>(is.getloc());
+        std::tm tm{};
+#endif
+        const CharT* command = nullptr;
+        auto modified = CharT{};
+        auto width = -1;
+
+        CONSTDATA int not_a_year = numeric_limits<int>::min();
+        CONSTDATA int not_a_2digit_year = 100;
+        CONSTDATA int not_a_century = not_a_year / 100;
+        CONSTDATA int not_a_month = 0;
+        CONSTDATA int not_a_day = 0;
+        CONSTDATA int not_a_hour = numeric_limits<int>::min();
+        CONSTDATA int not_a_hour_12_value = 0;
+        CONSTDATA int not_a_minute = not_a_hour;
+        CONSTDATA Duration not_a_second = Duration::min();
+        CONSTDATA int not_a_doy = -1;
+        CONSTDATA int not_a_weekday = 8;
+        CONSTDATA int not_a_week_num = 100;
+        CONSTDATA int not_a_ampm = -1;
+        CONSTDATA minutes not_a_offset = minutes::min();
+
+        int Y = not_a_year;             // c, F, Y                   *
+        int y = not_a_2digit_year;      // D, x, y                   *
+        int g = not_a_2digit_year;      // g                         *
+        int G = not_a_year;             // G                         *
+        int C = not_a_century;          // C                         *
+        int m = not_a_month;            // b, B, h, m, c, D, F, x    *
+        int d = not_a_day;              // c, d, D, e, F, x          *
+        int j = not_a_doy;              // j                         *
+        int wd = not_a_weekday;         // a, A, u, w                *
+        int H = not_a_hour;             // c, H, R, T, X             *
+        int I = not_a_hour_12_value;    // I, r                      *
+        int p = not_a_ampm;             // p, r                      *
+        int M = not_a_minute;           // c, M, r, R, T, X          *
+        Duration s = not_a_second;      // c, r, S, T, X             *
+        int U = not_a_week_num;         // U                         *
+        int V = not_a_week_num;         // V                         *
+        int W = not_a_week_num;         // W                         *
+        std::basic_string<CharT, Traits, Alloc> temp_abbrev;  // Z   *
+        minutes temp_offset = not_a_offset;  // z                    *
+
+        using detail::read;
+        using detail::rs;
+        using detail::ru;
+        using detail::rld;
+        using detail::checked_set;
+        for (; *fmt != CharT{} && !is.fail(); ++fmt)
+        {
+            switch (*fmt)
+            {
+            case 'a':
+            case 'A':
+            case 'u':
+            case 'w':  // wd:  a, A, u, w
+                if (command)
+                {
+                    int trial_wd = not_a_weekday;
+                    if (*fmt == 'a' || *fmt == 'A')
+                    {
+                        if (modified == CharT{})
+                        {
+#if !ONLY_C_LOCALE
+                            ios::iostate err = ios::goodbit;
+                            f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                            is.setstate(err);
+                            if (!is.fail())
+                                trial_wd = tm.tm_wday;
+#else
+                            auto nm = detail::weekday_names();
+                            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
+                            if (!is.fail())
+                                trial_wd = i % 7;
+#endif
+                        }
+                        else
+                            read(is, CharT{'%'}, width, modified, *fmt);
+                    }
+                    else  // *fmt == 'u' || *fmt == 'w'
+                    {
+#if !ONLY_C_LOCALE
+                        if (modified == CharT{})
+#else
+                        if (modified != CharT{'E'})
+#endif
+                        {
+                            read(is, ru{trial_wd, 1, width == -1 ?
+                                                      1u : static_cast<unsigned>(width)});
+                            if (!is.fail())
+                            {
+                                if (*fmt == 'u')
+                                {
+                                    if (!(1 <= trial_wd && trial_wd <= 7))
+                                    {
+                                        trial_wd = not_a_weekday;
+                                        is.setstate(ios::failbit);
+                                    }
+                                    else if (trial_wd == 7)
+                                        trial_wd = 0;
+                                }
+                                else  // *fmt == 'w'
+                                {
+                                    if (!(0 <= trial_wd && trial_wd <= 6))
+                                    {
+                                        trial_wd = not_a_weekday;
+                                        is.setstate(ios::failbit);
+                                    }
+                                }
+                            }
+                        }
+#if !ONLY_C_LOCALE
+                        else if (modified == CharT{'O'})
+                        {
+                            ios::iostate err = ios::goodbit;
+                            f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                            is.setstate(err);
+                            if (!is.fail())
+                                trial_wd = tm.tm_wday;
+                        }
+#endif
+                        else
+                            read(is, CharT{'%'}, width, modified, *fmt);
+                    }
+                    if (trial_wd != not_a_weekday)
+                        checked_set(wd, trial_wd, not_a_weekday, is);
+                }
+                else  // !command
+                    read(is, *fmt);
+                command = nullptr;
+                width = -1;
+                modified = CharT{};
+                break;
+            case 'b':
+            case 'B':
+            case 'h':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int ttm = not_a_month;
+#if !ONLY_C_LOCALE
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                            ttm = tm.tm_mon + 1;
+                        is.setstate(err);
+#else
+                        auto nm = detail::month_names();
+                        auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
+                        if (!is.fail())
+                            ttm = i % 12 + 1;
+#endif
+                        checked_set(m, ttm, not_a_month, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'c':
+                if (command)
+                {
+                    if (modified != CharT{'O'})
+                    {
+#if !ONLY_C_LOCALE
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                        {
+                            checked_set(Y, tm.tm_year + 1900, not_a_year, is);
+                            checked_set(m, tm.tm_mon + 1, not_a_month, is);
+                            checked_set(d, tm.tm_mday, not_a_day, is);
+                            checked_set(H, tm.tm_hour, not_a_hour, is);
+                            checked_set(M, tm.tm_min, not_a_minute, is);
+                            checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
+                                        not_a_second, is);
+                        }
+                        is.setstate(err);
+#else
+                        // "%a %b %e %T %Y"
+                        auto nm = detail::weekday_names();
+                        auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
+                        checked_set(wd, static_cast<int>(i % 7), not_a_weekday, is);
+                        ws(is);
+                        nm = detail::month_names();
+                        i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
+                        checked_set(m, static_cast<int>(i % 12 + 1), not_a_month, is);
+                        ws(is);
+                        int td = not_a_day;
+                        read(is, rs{td, 1, 2});
+                        checked_set(d, td, not_a_day, is);
+                        ws(is);
+                        using dfs = detail::decimal_format_seconds<Duration>;
+                        CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
+                        int tH;
+                        int tM;
+                        long double S;
+                        read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
+                                               CharT{':'}, rld{S, 1, w});
+                        checked_set(H, tH, not_a_hour, is);
+                        checked_set(M, tM, not_a_minute, is);
+                        checked_set(s, round<Duration>(duration<long double>{S}),
+                                    not_a_second, is);
+                        ws(is);
+                        int tY = not_a_year;
+                        read(is, rs{tY, 1, 4u});
+                        checked_set(Y, tY, not_a_year, is);
+#endif
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'x':
+                if (command)
+                {
+                    if (modified != CharT{'O'})
+                    {
+#if !ONLY_C_LOCALE
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                        {
+                            checked_set(Y, tm.tm_year + 1900, not_a_year, is);
+                            checked_set(m, tm.tm_mon + 1, not_a_month, is);
+                            checked_set(d, tm.tm_mday, not_a_day, is);
+                        }
+                        is.setstate(err);
+#else
+                        // "%m/%d/%y"
+                        int ty = not_a_2digit_year;
+                        int tm = not_a_month;
+                        int td = not_a_day;
+                        read(is, ru{tm, 1, 2}, CharT{'/'}, ru{td, 1, 2}, CharT{'/'},
+                                 rs{ty, 1, 2});
+                        checked_set(y, ty, not_a_2digit_year, is);
+                        checked_set(m, tm, not_a_month, is);
+                        checked_set(d, td, not_a_day, is);
+#endif
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'X':
+                if (command)
+                {
+                    if (modified != CharT{'O'})
+                    {
+#if !ONLY_C_LOCALE
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                        {
+                            checked_set(H, tm.tm_hour, not_a_hour, is);
+                            checked_set(M, tm.tm_min, not_a_minute, is);
+                            checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
+                                        not_a_second, is);
+                        }
+                        is.setstate(err);
+#else
+                        // "%T"
+                        using dfs = detail::decimal_format_seconds<Duration>;
+                        CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
+                        int tH = not_a_hour;
+                        int tM = not_a_minute;
+                        long double S;
+                        read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
+                                               CharT{':'}, rld{S, 1, w});
+                        checked_set(H, tH, not_a_hour, is);
+                        checked_set(M, tM, not_a_minute, is);
+                        checked_set(s, round<Duration>(duration<long double>{S}),
+                                    not_a_second, is);
+#endif
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'C':
+                if (command)
+                {
+                    int tC = not_a_century;
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+                    {
+#endif
+                        read(is, rs{tC, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+#if !ONLY_C_LOCALE
+                    }
+                    else
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                        {
+                            auto tY = tm.tm_year + 1900;
+                            tC = (tY >= 0 ? tY : tY-99) / 100;
+                        }
+                        is.setstate(err);
+                    }
+#endif
+                    checked_set(C, tC, not_a_century, is);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'D':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tn = not_a_month;
+                        int td = not_a_day;
+                        int ty = not_a_2digit_year;
+                        read(is, ru{tn, 1, 2}, CharT{'\0'}, CharT{'/'}, CharT{'\0'},
+                                 ru{td, 1, 2}, CharT{'\0'}, CharT{'/'}, CharT{'\0'},
+                                 rs{ty, 1, 2});
+                        checked_set(y, ty, not_a_2digit_year, is);
+                        checked_set(m, tn, not_a_month, is);
+                        checked_set(d, td, not_a_day, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'F':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tY = not_a_year;
+                        int tn = not_a_month;
+                        int td = not_a_day;
+                        read(is, rs{tY, 1, width == -1 ? 4u : static_cast<unsigned>(width)},
+                                 CharT{'-'}, ru{tn, 1, 2}, CharT{'-'}, ru{td, 1, 2});
+                        checked_set(Y, tY, not_a_year, is);
+                        checked_set(m, tn, not_a_month, is);
+                        checked_set(d, td, not_a_day, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'd':
+            case 'e':
+                if (command)
+                {
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#else
+                    if (modified != CharT{'E'})
+#endif
+                    {
+                        int td = not_a_day;
+                        read(is, rs{td, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(d, td, not_a_day, is);
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        command = nullptr;
+                        width = -1;
+                        modified = CharT{};
+                        if ((err & ios::failbit) == 0)
+                            checked_set(d, tm.tm_mday, not_a_day, is);
+                        is.setstate(err);
+                    }
+#endif
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'H':
+                if (command)
+                {
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#else
+                    if (modified != CharT{'E'})
+#endif
+                    {
+                        int tH = not_a_hour;
+                        read(is, ru{tH, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(H, tH, not_a_hour, is);
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                            checked_set(H, tm.tm_hour, not_a_hour, is);
+                        is.setstate(err);
+                    }
+#endif
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'I':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tI = not_a_hour_12_value;
+                        // reads in an hour into I, but most be in [1, 12]
+                        read(is, rs{tI, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        if (!(1 <= tI && tI <= 12))
+                            is.setstate(ios::failbit);
+                        checked_set(I, tI, not_a_hour_12_value, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+               break;
+            case 'j':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tj = not_a_doy;
+                        read(is, ru{tj, 1, width == -1 ? 3u : static_cast<unsigned>(width)});
+                        checked_set(j, tj, not_a_doy, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'M':
+                if (command)
+                {
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#else
+                    if (modified != CharT{'E'})
+#endif
+                    {
+                        int tM = not_a_minute;
+                        read(is, ru{tM, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(M, tM, not_a_minute, is);
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                            checked_set(M, tm.tm_min, not_a_minute, is);
+                        is.setstate(err);
+                    }
+#endif
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'm':
+                if (command)
+                {
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#else
+                    if (modified != CharT{'E'})
+#endif
+                    {
+                        int tn = not_a_month;
+                        read(is, rs{tn, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(m, tn, not_a_month, is);
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                            checked_set(m, tm.tm_mon + 1, not_a_month, is);
+                        is.setstate(err);
+                    }
+#endif
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'n':
+            case 't':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        // %n matches a single white space character
+                        // %t matches 0 or 1 white space characters
+                        auto ic = is.peek();
+                        if (Traits::eq_int_type(ic, Traits::eof()))
+                        {
+                            ios::iostate err = ios::eofbit;
+                            if (*fmt == 'n')
+                                err |= ios::failbit;
+                            is.setstate(err);
+                            break;
+                        }
+                        if (isspace(ic))
+                        {
+                            (void)is.get();
+                        }
+                        else if (*fmt == 'n')
+                            is.setstate(ios::failbit);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'p':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tp = not_a_ampm;
+#if !ONLY_C_LOCALE
+                        tm = std::tm{};
+                        tm.tm_hour = 1;
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        is.setstate(err);
+                        if (tm.tm_hour == 1)
+                            tp = 0;
+                        else if (tm.tm_hour == 13)
+                            tp = 1;
+                        else
+                            is.setstate(err);
+#else
+                        auto nm = detail::ampm_names();
+                        auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
+                        tp = i;
+#endif
+                        checked_set(p, tp, not_a_ampm, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+
+               break;
+            case 'r':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+#if !ONLY_C_LOCALE
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                        {
+                            checked_set(H, tm.tm_hour, not_a_hour, is);
+                            checked_set(M, tm.tm_min, not_a_hour, is);
+                            checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
+                                        not_a_second, is);
+                        }
+                        is.setstate(err);
+#else
+                        // "%I:%M:%S %p"
+                        using dfs = detail::decimal_format_seconds<Duration>;
+                        CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
+                        long double S;
+                        int tI = not_a_hour_12_value;
+                        int tM = not_a_minute;
+                        read(is, ru{tI, 1, 2}, CharT{':'}, ru{tM, 1, 2},
+                                               CharT{':'}, rld{S, 1, w});
+                        checked_set(I, tI, not_a_hour_12_value, is);
+                        checked_set(M, tM, not_a_minute, is);
+                        checked_set(s, round<Duration>(duration<long double>{S}),
+                                    not_a_second, is);
+                        ws(is);
+                        auto nm = detail::ampm_names();
+                        auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
+                        checked_set(p, static_cast<int>(i), not_a_ampm, is);
+#endif
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'R':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tH = not_a_hour;
+                        int tM = not_a_minute;
+                        read(is, ru{tH, 1, 2}, CharT{'\0'}, CharT{':'}, CharT{'\0'},
+                                 ru{tM, 1, 2}, CharT{'\0'});
+                        checked_set(H, tH, not_a_hour, is);
+                        checked_set(M, tM, not_a_minute, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'S':
+                if (command)
+                {
+ #if !ONLY_C_LOCALE
+                   if (modified == CharT{})
+#else
+                   if (modified != CharT{'E'})
+#endif
+                    {
+                        using dfs = detail::decimal_format_seconds<Duration>;
+                        CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
+                        long double S;
+                        read(is, rld{S, 1, width == -1 ? w : static_cast<unsigned>(width)});
+                        checked_set(s, round<Duration>(duration<long double>{S}),
+                                    not_a_second, is);
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'O'})
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                            checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
+                                        not_a_second, is);
+                        is.setstate(err);
+                    }
+#endif
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'T':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        using dfs = detail::decimal_format_seconds<Duration>;
+                        CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
+                        int tH = not_a_hour;
+                        int tM = not_a_minute;
+                        long double S;
+                        read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
+                                               CharT{':'}, rld{S, 1, w});
+                        checked_set(H, tH, not_a_hour, is);
+                        checked_set(M, tM, not_a_minute, is);
+                        checked_set(s, round<Duration>(duration<long double>{S}),
+                                    not_a_second, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'Y':
+                if (command)
+                {
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#else
+                    if (modified != CharT{'O'})
+#endif
+                    {
+                        int tY = not_a_year;
+                        read(is, rs{tY, 1, width == -1 ? 4u : static_cast<unsigned>(width)});
+                        checked_set(Y, tY, not_a_year, is);
+                    }
+#if !ONLY_C_LOCALE
+                    else if (modified == CharT{'E'})
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                            checked_set(Y, tm.tm_year + 1900, not_a_year, is);
+                        is.setstate(err);
+                    }
+#endif
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'y':
+                if (command)
+                {
+#if !ONLY_C_LOCALE
+                    if (modified == CharT{})
+#endif
+                    {
+                        int ty = not_a_2digit_year;
+                        read(is, ru{ty, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(y, ty, not_a_2digit_year, is);
+                    }
+#if !ONLY_C_LOCALE
+                    else
+                    {
+                        ios::iostate err = ios::goodbit;
+                        f.get(is, nullptr, is, err, &tm, command, fmt+1);
+                        if ((err & ios::failbit) == 0)
+                            checked_set(Y, tm.tm_year + 1900, not_a_year, is);
+                        is.setstate(err);
+                    }
+#endif
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'g':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tg = not_a_2digit_year;
+                        read(is, ru{tg, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(g, tg, not_a_2digit_year, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'G':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tG = not_a_year;
+                        read(is, rs{tG, 1, width == -1 ? 4u : static_cast<unsigned>(width)});
+                        checked_set(G, tG, not_a_year, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'U':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tU = not_a_week_num;
+                        read(is, ru{tU, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(U, tU, not_a_week_num, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'V':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tV = not_a_week_num;
+                        read(is, ru{tV, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(V, tV, not_a_week_num, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'W':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        int tW = not_a_week_num;
+                        read(is, ru{tW, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
+                        checked_set(W, tW, not_a_week_num, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'E':
+            case 'O':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        modified = *fmt;
+                    }
+                    else
+                    {
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                        command = nullptr;
+                        width = -1;
+                        modified = CharT{};
+                    }
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case '%':
+                if (command)
+                {
+                    if (modified == CharT{})
+                        read(is, *fmt);
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    command = fmt;
+                break;
+            case 'z':
+                if (command)
+                {
+                    int tH, tM;
+                    minutes toff = not_a_offset;
+                    bool neg = false;
+                    auto ic = is.peek();
+                    if (!Traits::eq_int_type(ic, Traits::eof()))
+                    {
+                        auto c = static_cast<char>(Traits::to_char_type(ic));
+                        if (c == '-')
+                            neg = true;
+                    }
+                    if (modified == CharT{})
+                    {
+                        read(is, rs{tH, 2, 2});
+                        if (!is.fail())
+                            toff = hours{std::abs(tH)};
+                        if (is.good())
+                        {
+                            ic = is.peek();
+                            if (!Traits::eq_int_type(ic, Traits::eof()))
+                            {
+                                auto c = static_cast<char>(Traits::to_char_type(ic));
+                                if ('0' <= c && c <= '9')
+                                {
+                                    read(is, ru{tM, 2, 2});
+                                    if (!is.fail())
+                                        toff += minutes{tM};
+                                }
+                            }
+                        }
+                    }
+                    else
+                    {
+                        read(is, rs{tH, 1, 2});
+                        if (!is.fail())
+                            toff = hours{std::abs(tH)};
+                        if (is.good())
+                        {
+                            ic = is.peek();
+                            if (!Traits::eq_int_type(ic, Traits::eof()))
+                            {
+                                auto c = static_cast<char>(Traits::to_char_type(ic));
+                                if (c == ':')
+                                {
+                                    (void)is.get();
+                                    read(is, ru{tM, 2, 2});
+                                    if (!is.fail())
+                                        toff += minutes{tM};
+                                }
+                            }
+                        }
+                    }
+                    if (neg)
+                        toff = -toff;
+                    checked_set(temp_offset, toff, not_a_offset, is);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            case 'Z':
+                if (command)
+                {
+                    if (modified == CharT{})
+                    {
+                        std::basic_string<CharT, Traits, Alloc> buf;
+                        while (is.rdstate() == std::ios::goodbit)
+                        {
+                            auto i = is.rdbuf()->sgetc();
+                            if (Traits::eq_int_type(i, Traits::eof()))
+                            {
+                                is.setstate(ios::eofbit);
+                                break;
+                            }
+                            auto wc = Traits::to_char_type(i);
+                            auto c = static_cast<char>(wc);
+                            // is c a valid time zone name or abbreviation character?
+                            if (!(CharT{1} < wc && wc < CharT{127}) || !(isalnum(c) ||
+                                    c == '_' || c == '/' || c == '-' || c == '+'))
+                                break;
+                            buf.push_back(c);
+                            is.rdbuf()->sbumpc();
+                        }
+                        if (buf.empty())
+                            is.setstate(ios::failbit);
+                        checked_set(temp_abbrev, buf, {}, is);
+                    }
+                    else
+                        read(is, CharT{'%'}, width, modified, *fmt);
+                    command = nullptr;
+                    width = -1;
+                    modified = CharT{};
+                }
+                else
+                    read(is, *fmt);
+                break;
+            default:
+                if (command)
+                {
+                    if (width == -1 && modified == CharT{} && '0' <= *fmt && *fmt <= '9')
+                    {
+                        width = static_cast<char>(*fmt) - '0';
+                        while ('0' <= fmt[1] && fmt[1] <= '9')
+                            width = 10*width + static_cast<char>(*++fmt) - '0';
+                    }
+                    else
+                    {
+                        if (modified == CharT{})
+                            read(is, CharT{'%'}, width, *fmt);
+                        else
+                            read(is, CharT{'%'}, width, modified, *fmt);
+                        command = nullptr;
+                        width = -1;
+                        modified = CharT{};
+                    }
+                }
+                else  // !command
+                {
+                    if (isspace(static_cast<unsigned char>(*fmt)))
+                    {
+                        // space matches 0 or more white space characters
+                        if (is.good())
+                           ws(is);
+                    }
+                    else
+                        read(is, *fmt);
+                }
+                break;
+            }
+        }
+        // is.fail() || *fmt == CharT{}
+        if (is.rdstate() == ios::goodbit && command)
+        {
+            if (modified == CharT{})
+                read(is, CharT{'%'}, width);
+            else
+                read(is, CharT{'%'}, width, modified);
+        }
+        if (!is.fail())
+        {
+            if (y != not_a_2digit_year)
+            {
+                // Convert y and an optional C to Y
+                if (!(0 <= y && y <= 99))
+                    goto broken;
+                if (C == not_a_century)
+                {
+                    if (Y == not_a_year)
+                    {
+                        if (y >= 69)
+                            C = 19;
+                        else
+                            C = 20;
+                    }
+                    else
+                    {
+                        C = (Y >= 0 ? Y : Y-100) / 100;
+                    }
+                }
+                int tY;
+                if (C >= 0)
+                    tY = 100*C + y;
+                else
+                    tY = 100*(C+1) - (y == 0 ? 100 : y);
+                if (Y != not_a_year && Y != tY)
+                    goto broken;
+                Y = tY;
+            }
+            if (g != not_a_2digit_year)
+            {
+                // Convert g and an optional C to G
+                if (!(0 <= g && g <= 99))
+                    goto broken;
+                if (C == not_a_century)
+                {
+                    if (G == not_a_year)
+                    {
+                        if (g >= 69)
+                            C = 19;
+                        else
+                            C = 20;
+                    }
+                    else
+                    {
+                        C = (G >= 0 ? G : G-100) / 100;
+                    }
+                }
+                int tG;
+                if (C >= 0)
+                    tG = 100*C + g;
+                else
+                    tG = 100*(C+1) - (g == 0 ? 100 : g);
+                if (G != not_a_year && G != tG)
+                    goto broken;
+                G = tG;
+            }
+            if (Y < static_cast<int>(year::min()) || Y > static_cast<int>(year::max()))
+                Y = not_a_year;
+            bool computed = false;
+            if (G != not_a_year && V != not_a_week_num && wd != not_a_weekday)
+            {
+                year_month_day ymd_trial = sys_days(year{G-1}/December/Thursday[last]) +
+                                           (Monday-Thursday) + weeks{V-1} +
+                                           (weekday{static_cast<unsigned>(wd)}-Monday);
+                if (Y == not_a_year)
+                    Y = static_cast<int>(ymd_trial.year());
+                else if (year{Y} != ymd_trial.year())
+                    goto broken;
+                if (m == not_a_month)
+                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
+                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
+                    goto broken;
+                if (d == not_a_day)
+                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
+                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
+                    goto broken;
+                computed = true;
+            }
+            if (Y != not_a_year && U != not_a_week_num && wd != not_a_weekday)
+            {
+                year_month_day ymd_trial = sys_days(year{Y}/January/Sunday[1]) +
+                                           weeks{U-1} +
+                                           (weekday{static_cast<unsigned>(wd)} - Sunday);
+                if (Y == not_a_year)
+                    Y = static_cast<int>(ymd_trial.year());
+                else if (year{Y} != ymd_trial.year())
+                    goto broken;
+                if (m == not_a_month)
+                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
+                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
+                    goto broken;
+                if (d == not_a_day)
+                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
+                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
+                    goto broken;
+                computed = true;
+            }
+            if (Y != not_a_year && W != not_a_week_num && wd != not_a_weekday)
+            {
+                year_month_day ymd_trial = sys_days(year{Y}/January/Monday[1]) +
+                                           weeks{W-1} +
+                                           (weekday{static_cast<unsigned>(wd)} - Monday);
+                if (Y == not_a_year)
+                    Y = static_cast<int>(ymd_trial.year());
+                else if (year{Y} != ymd_trial.year())
+                    goto broken;
+                if (m == not_a_month)
+                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
+                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
+                    goto broken;
+                if (d == not_a_day)
+                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
+                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
+                    goto broken;
+                computed = true;
+            }
+            if (j != not_a_doy && Y != not_a_year)
+            {
+                auto ymd_trial = year_month_day{local_days(year{Y}/1/1) + days{j-1}};
+                if (m == 0)
+                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
+                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
+                    goto broken;
+                if (d == 0)
+                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
+                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
+                    goto broken;
+                j = not_a_doy;
+            }
+            auto ymd = year{Y}/m/d;
+            if (ymd.ok())
+            {
+                if (wd == not_a_weekday)
+                    wd = static_cast<int>((weekday(sys_days(ymd)) - Sunday).count());
+                else if (wd != static_cast<int>((weekday(sys_days(ymd)) - Sunday).count()))
+                    goto broken;
+                if (!computed)
+                {
+                    if (G != not_a_year || V != not_a_week_num)
+                    {
+                        sys_days sd = ymd;
+                        auto G_trial = year_month_day{sd + days{3}}.year();
+                        auto start = sys_days((G_trial - years{1})/December/Thursday[last]) +
+                                     (Monday - Thursday);
+                        if (sd < start)
+                        {
+                            --G_trial;
+                            if (V != not_a_week_num)
+                                start = sys_days((G_trial - years{1})/December/Thursday[last])
+                                        + (Monday - Thursday);
+                        }
+                        if (G != not_a_year && G != static_cast<int>(G_trial))
+                            goto broken;
+                        if (V != not_a_week_num)
+                        {
+                            auto V_trial = duration_cast<weeks>(sd - start).count() + 1;
+                            if (V != V_trial)
+                                goto broken;
+                        }
+                    }
+                    if (U != not_a_week_num)
+                    {
+                        auto start = sys_days(Sunday[1]/January/ymd.year());
+                        auto U_trial = floor<weeks>(sys_days(ymd) - start).count() + 1;
+                        if (U != U_trial)
+                            goto broken;
+                    }
+                    if (W != not_a_week_num)
+                    {
+                        auto start = sys_days(Monday[1]/January/ymd.year());
+                        auto W_trial = floor<weeks>(sys_days(ymd) - start).count() + 1;
+                        if (W != W_trial)
+                            goto broken;
+                    }
+                }
+            }
+            fds.ymd = ymd;
+            if (I != not_a_hour_12_value)
+            {
+                if (!(1 <= I && I <= 12))
+                    goto broken;
+                if (p != not_a_ampm)
+                {
+                    // p is in [0, 1] == [AM, PM]
+                    // Store trial H in I
+                    if (I == 12)
+                        --p;
+                    I += p*12;
+                    // Either set H from I or make sure H and I are consistent
+                    if (H == not_a_hour)
+                        H = I;
+                    else if (I != H)
+                        goto broken;
+                }
+                else  // p == not_a_ampm
+                {
+                    // if H, make sure H and I could be consistent
+                    if (H != not_a_hour)
+                    {
+                        if (I == 12)
+                        {
+                            if (H != 0 && H != 12)
+                                goto broken;
+                        }
+                        else if (!(I == H || I == H+12))
+                        {
+                            goto broken;
+                        }
+                    }
+                }
+            }
+            if (H != not_a_hour)
+            {
+                fds.has_tod = true;
+                fds.tod = hh_mm_ss<Duration>{hours{H}};
+            }
+            if (M != not_a_minute)
+            {
+                fds.has_tod = true;
+                fds.tod.m_ = minutes{M};
+            }
+            if (s != not_a_second)
+            {
+                fds.has_tod = true;
+                fds.tod.s_ = detail::decimal_format_seconds<Duration>{s};
+            }
+            if (j != not_a_doy)
+            {
+                fds.has_tod = true;
+                fds.tod.h_ += hours{days{j}};
+            }
+            if (wd != not_a_weekday)
+                fds.wd = weekday{static_cast<unsigned>(wd)};
+            if (abbrev != nullptr)
+                *abbrev = std::move(temp_abbrev);
+            if (offset != nullptr && temp_offset != not_a_offset)
+              *offset = temp_offset;
+        }
+       return is;
+    }
+broken:
+    is.setstate(ios::failbit);
+    return is;
+}
+
+template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt, year& y,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.ymd.year().ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        y = fds.ymd.year();
+    return is;
+}
+
+template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt, month& m,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.ymd.month().ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        m = fds.ymd.month();
+    return is;
+}
+
+template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt, day& d,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.ymd.day().ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        d = fds.ymd.day();
+    return is;
+}
+
+template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt, weekday& wd,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.wd.ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        wd = fds.wd;
+    return is;
+}
+
+template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt, year_month& ym,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.ymd.month().ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        ym = fds.ymd.year()/fds.ymd.month();
+    return is;
+}
+
+template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt, month_day& md,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.ymd.month().ok() || !fds.ymd.day().ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        md = fds.ymd.month()/fds.ymd.day();
+    return is;
+}
+
+template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            year_month_day& ymd, std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = std::chrono::seconds;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.ymd.ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        ymd = fds.ymd;
+    return is;
+}
+
+template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            sys_time<Duration>& tp, std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
+    std::chrono::minutes offset_local{};
+    auto offptr = offset ? offset : &offset_local;
+    fields<CT> fds{};
+    fds.has_tod = true;
+    from_stream(is, fmt, fds, abbrev, offptr);
+    if (!fds.ymd.ok() || !fds.tod.in_conventional_range())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        tp = round<Duration>(sys_days(fds.ymd) - *offptr + fds.tod.to_duration());
+    return is;
+}
+
+template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            local_time<Duration>& tp, std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
+    fields<CT> fds{};
+    fds.has_tod = true;
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.ymd.ok() || !fds.tod.in_conventional_range())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        tp = round<Duration>(local_seconds{local_days(fds.ymd)} + fds.tod.to_duration());
+    return is;
+}
+
+template <class Rep, class Period, class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            std::chrono::duration<Rep, Period>& d,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using Duration = std::chrono::duration<Rep, Period>;
+    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
+    fields<CT> fds{};
+    from_stream(is, fmt, fds, abbrev, offset);
+    if (!fds.has_tod)
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+        d = std::chrono::duration_cast<Duration>(fds.tod.to_duration());
+    return is;
+}
+
+template <class Parsable, class CharT, class Traits = std::char_traits<CharT>,
+          class Alloc = std::allocator<CharT>>
+struct parse_manip
+{
+    const std::basic_string<CharT, Traits, Alloc> format_;
+    Parsable&                                     tp_;
+    std::basic_string<CharT, Traits, Alloc>*      abbrev_;
+    std::chrono::minutes*                         offset_;
+
+public:
+    parse_manip(std::basic_string<CharT, Traits, Alloc> format, Parsable& tp,
+                std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+                std::chrono::minutes* offset = nullptr)
+        : format_(std::move(format))
+        , tp_(tp)
+        , abbrev_(abbrev)
+        , offset_(offset)
+        {}
+
+};
+
+template <class Parsable, class CharT, class Traits, class Alloc>
+std::basic_istream<CharT, Traits>&
+operator>>(std::basic_istream<CharT, Traits>& is,
+           const parse_manip<Parsable, CharT, Traits, Alloc>& x)
+{
+    return from_stream(is, x.format_.c_str(), x.tp_, x.abbrev_, x.offset_);
+}
+
+template <class Parsable, class CharT, class Traits, class Alloc>
+inline
+auto
+parse(const std::basic_string<CharT, Traits, Alloc>& format, Parsable& tp)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
+                            format.c_str(), tp),
+                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp})
+{
+    return {format, tp};
+}
+
+template <class Parsable, class CharT, class Traits, class Alloc>
+inline
+auto
+parse(const std::basic_string<CharT, Traits, Alloc>& format, Parsable& tp,
+      std::basic_string<CharT, Traits, Alloc>& abbrev)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
+                            format.c_str(), tp, &abbrev),
+                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev})
+{
+    return {format, tp, &abbrev};
+}
+
+template <class Parsable, class CharT, class Traits, class Alloc>
+inline
+auto
+parse(const std::basic_string<CharT, Traits, Alloc>& format, Parsable& tp,
+      std::chrono::minutes& offset)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
+                            format.c_str(), tp,
+                            std::declval<std::basic_string<CharT, Traits, Alloc>*>(),
+                            &offset),
+                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, nullptr, &offset})
+{
+    return {format, tp, nullptr, &offset};
+}
+
+template <class Parsable, class CharT, class Traits, class Alloc>
+inline
+auto
+parse(const std::basic_string<CharT, Traits, Alloc>& format, Parsable& tp,
+      std::basic_string<CharT, Traits, Alloc>& abbrev, std::chrono::minutes& offset)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(),
+                            format.c_str(), tp, &abbrev, &offset),
+                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev, &offset})
+{
+    return {format, tp, &abbrev, &offset};
+}
+
+// const CharT* formats
+
+template <class Parsable, class CharT>
+inline
+auto
+parse(const CharT* format, Parsable& tp)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT>&>(), format, tp),
+                parse_manip<Parsable, CharT>{format, tp})
+{
+    return {format, tp};
+}
+
+template <class Parsable, class CharT, class Traits, class Alloc>
+inline
+auto
+parse(const CharT* format, Parsable& tp, std::basic_string<CharT, Traits, Alloc>& abbrev)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(), format,
+                            tp, &abbrev),
+                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev})
+{
+    return {format, tp, &abbrev};
+}
+
+template <class Parsable, class CharT>
+inline
+auto
+parse(const CharT* format, Parsable& tp, std::chrono::minutes& offset)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT>&>(), format,
+                            tp, std::declval<std::basic_string<CharT>*>(), &offset),
+                parse_manip<Parsable, CharT>{format, tp, nullptr, &offset})
+{
+    return {format, tp, nullptr, &offset};
+}
+
+template <class Parsable, class CharT, class Traits, class Alloc>
+inline
+auto
+parse(const CharT* format, Parsable& tp,
+      std::basic_string<CharT, Traits, Alloc>& abbrev, std::chrono::minutes& offset)
+    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits>&>(), format,
+                            tp, &abbrev, &offset),
+                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev, &offset})
+{
+    return {format, tp, &abbrev, &offset};
+}
+
+// duration streaming
+
+template <class CharT, class Traits, class Rep, class Period>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os,
+           const std::chrono::duration<Rep, Period>& d)
+{
+    return os << detail::make_string<CharT, Traits>::from(d.count()) +
+                 detail::get_units<CharT>(typename Period::type{});
+}
+
+}  // namespace date
+
+#ifdef _MSC_VER
+#   pragma warning(pop)
+#endif
+
+#ifdef __GNUC__
+# pragma GCC diagnostic pop
+#endif
+
+#endif  // DATE_H
diff --git a/src/libs/date/includes/date/ios.h b/src/libs/date/includes/date/ios.h
new file mode 100644
index 00000000..ee54b9d0
--- /dev/null
+++ b/src/libs/date/includes/date/ios.h
@@ -0,0 +1,50 @@
+//
+//  ios.h
+//  DateTimeLib
+//
+// The MIT License (MIT)
+//
+// Copyright (c) 2016 Alexander Kormanovsky
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#ifndef ios_hpp
+#define ios_hpp
+
+#if __APPLE__
+# include <TargetConditionals.h>
+# if TARGET_OS_IPHONE
+#   include <string>
+
+    namespace date
+    {
+    namespace iOSUtils
+    {
+    
+    std::string get_tzdata_path();
+    std::string get_current_timezone();
+    
+    }  // namespace iOSUtils
+    }  // namespace date
+
+# endif  // TARGET_OS_IPHONE
+#else   // !__APPLE__
+# define TARGET_OS_IPHONE 0
+#endif  // !__APPLE__
+#endif // ios_hpp
diff --git a/src/libs/date/includes/date/islamic.h b/src/libs/date/includes/date/islamic.h
new file mode 100644
index 00000000..82ed6597
--- /dev/null
+++ b/src/libs/date/includes/date/islamic.h
@@ -0,0 +1,3031 @@
+#ifndef ISLAMIC_H
+#define ISLAMIC_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2016 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+#include "date.h"
+
+namespace islamic
+{
+
+// durations
+
+using days = date::days;
+
+using weeks = date::weeks;
+
+using years = std::chrono::duration
+    <int, date::detail::ratio_multiply<std::ratio<10631, 30>, days::period>>;
+
+using months = std::chrono::duration
+    <int, date::detail::ratio_divide<years::period, std::ratio<12>>>;
+
+// time_point
+
+using sys_days   = date::sys_days;
+using local_days = date::local_days;
+
+// types
+
+struct last_spec
+{
+    explicit last_spec() = default;
+};
+
+class day;
+class month;
+class year;
+
+class weekday;
+class weekday_indexed;
+class weekday_last;
+
+class month_day;
+class month_day_last;
+class month_weekday;
+class month_weekday_last;
+
+class year_month;
+
+class year_month_day;
+class year_month_day_last;
+class year_month_weekday;
+class year_month_weekday_last;
+
+// date composition operators
+
+CONSTCD11 year_month operator/(const year& y, const month& m) NOEXCEPT;
+CONSTCD11 year_month operator/(const year& y, int          m) NOEXCEPT;
+
+CONSTCD11 month_day operator/(const day& d, const month& m) NOEXCEPT;
+CONSTCD11 month_day operator/(const day& d, int          m) NOEXCEPT;
+CONSTCD11 month_day operator/(const month& m, const day& d) NOEXCEPT;
+CONSTCD11 month_day operator/(const month& m, int        d) NOEXCEPT;
+CONSTCD11 month_day operator/(int          m, const day& d) NOEXCEPT;
+
+CONSTCD11 month_day_last operator/(const month& m, last_spec) NOEXCEPT;
+CONSTCD11 month_day_last operator/(int          m, last_spec) NOEXCEPT;
+CONSTCD11 month_day_last operator/(last_spec, const month& m) NOEXCEPT;
+CONSTCD11 month_day_last operator/(last_spec, int          m) NOEXCEPT;
+
+CONSTCD11 month_weekday operator/(const month& m, const weekday_indexed& wdi) NOEXCEPT;
+CONSTCD11 month_weekday operator/(int          m, const weekday_indexed& wdi) NOEXCEPT;
+CONSTCD11 month_weekday operator/(const weekday_indexed& wdi, const month& m) NOEXCEPT;
+CONSTCD11 month_weekday operator/(const weekday_indexed& wdi, int          m) NOEXCEPT;
+
+CONSTCD11 month_weekday_last operator/(const month& m, const weekday_last& wdl) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(int          m, const weekday_last& wdl) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(const weekday_last& wdl, const month& m) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(const weekday_last& wdl, int          m) NOEXCEPT;
+
+CONSTCD11 year_month_day operator/(const year_month& ym, const day& d) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const year_month& ym, int        d) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const year& y, const month_day& md) NOEXCEPT;
+CONSTCD11 year_month_day operator/(int         y, const month_day& md) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const month_day& md, const year& y) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const month_day& md, int         y) NOEXCEPT;
+
+CONSTCD11
+    year_month_day_last operator/(const year_month& ym,   last_spec) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const year& y, const month_day_last& mdl) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(int         y, const month_day_last& mdl) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const month_day_last& mdl, const year& y) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const month_day_last& mdl, int         y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const year_month& ym, const weekday_indexed& wdi) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const year&        y, const month_weekday&   mwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(int                y, const month_weekday&   mwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const month_weekday& mwd, const year&          y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const month_weekday& mwd, int                  y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const year_month& ym, const weekday_last& wdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const year& y, const month_weekday_last& mwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(int         y, const month_weekday_last& mwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, const year& y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, int         y) NOEXCEPT;
+
+// Detailed interface
+
+// day
+
+class day
+{
+    unsigned char d_;
+
+public:
+    explicit CONSTCD11 day(unsigned d) NOEXCEPT;
+
+    CONSTCD14 day& operator++()    NOEXCEPT;
+    CONSTCD14 day  operator++(int) NOEXCEPT;
+    CONSTCD14 day& operator--()    NOEXCEPT;
+    CONSTCD14 day  operator--(int) NOEXCEPT;
+
+    CONSTCD14 day& operator+=(const days& d) NOEXCEPT;
+    CONSTCD14 day& operator-=(const days& d) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const day& x, const day& y) NOEXCEPT;
+
+CONSTCD11 day  operator+(const day&  x, const days& y) NOEXCEPT;
+CONSTCD11 day  operator+(const days& x, const day&  y) NOEXCEPT;
+CONSTCD11 day  operator-(const day&  x, const days& y) NOEXCEPT;
+CONSTCD11 days operator-(const day&  x, const day&  y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const day& d);
+
+// month
+
+class month
+{
+    unsigned char m_;
+
+public:
+    explicit CONSTCD11 month(unsigned m) NOEXCEPT;
+
+    CONSTCD14 month& operator++()    NOEXCEPT;
+    CONSTCD14 month  operator++(int) NOEXCEPT;
+    CONSTCD14 month& operator--()    NOEXCEPT;
+    CONSTCD14 month  operator--(int) NOEXCEPT;
+
+    CONSTCD14 month& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 month& operator-=(const months& m) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month& x, const month& y) NOEXCEPT;
+
+CONSTCD14 month  operator+(const month&  x, const months& y) NOEXCEPT;
+CONSTCD14 month  operator+(const months& x,  const month& y) NOEXCEPT;
+CONSTCD14 month  operator-(const month&  x, const months& y) NOEXCEPT;
+CONSTCD14 months operator-(const month&  x,  const month& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month& m);
+
+// year
+
+class year
+{
+    short y_;
+
+public:
+    explicit CONSTCD11 year(int y) NOEXCEPT;
+
+    CONSTCD14 year& operator++()    NOEXCEPT;
+    CONSTCD14 year  operator++(int) NOEXCEPT;
+    CONSTCD14 year& operator--()    NOEXCEPT;
+    CONSTCD14 year  operator--(int) NOEXCEPT;
+
+    CONSTCD14 year& operator+=(const years& y) NOEXCEPT;
+    CONSTCD14 year& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD14 bool is_leap() const NOEXCEPT;
+
+    CONSTCD11 explicit operator int() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+    static CONSTCD11 year min() NOEXCEPT;
+    static CONSTCD11 year max() NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year& x, const year& y) NOEXCEPT;
+
+CONSTCD11 year  operator+(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 year  operator+(const years& x, const year&  y) NOEXCEPT;
+CONSTCD11 year  operator-(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 years operator-(const year&  x, const year&  y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y);
+
+// weekday
+
+class weekday
+{
+    unsigned char wd_;
+public:
+    explicit CONSTCD11 weekday(unsigned wd) NOEXCEPT;
+    explicit weekday(int) = delete;
+    CONSTCD11 weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD11 explicit weekday(const local_days& dp) NOEXCEPT;
+
+    CONSTCD14 weekday& operator++()    NOEXCEPT;
+    CONSTCD14 weekday  operator++(int) NOEXCEPT;
+    CONSTCD14 weekday& operator--()    NOEXCEPT;
+    CONSTCD14 weekday  operator--(int) NOEXCEPT;
+
+    CONSTCD14 weekday& operator+=(const days& d) NOEXCEPT;
+    CONSTCD14 weekday& operator-=(const days& d) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+    CONSTCD11 weekday_indexed operator[](unsigned index) const NOEXCEPT;
+    CONSTCD11 weekday_last    operator[](last_spec)      const NOEXCEPT;
+
+private:
+    static CONSTCD11 unsigned char weekday_from_days(int z) NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday& x, const weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday& x, const weekday& y) NOEXCEPT;
+
+CONSTCD14 weekday operator+(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 weekday operator+(const days&    x, const weekday& y) NOEXCEPT;
+CONSTCD14 weekday operator-(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 days    operator-(const weekday& x, const weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd);
+
+// weekday_indexed
+
+class weekday_indexed
+{
+    unsigned char wd_    : 4;
+    unsigned char index_ : 4;
+
+public:
+    CONSTCD11 weekday_indexed(const islamic::weekday& wd, unsigned index) NOEXCEPT;
+
+    CONSTCD11 islamic::weekday weekday() const NOEXCEPT;
+    CONSTCD11 unsigned index() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_indexed& wdi);
+
+// weekday_last
+
+class weekday_last
+{
+    islamic::weekday wd_;
+
+public:
+    explicit CONSTCD11 weekday_last(const islamic::weekday& wd) NOEXCEPT;
+
+    CONSTCD11 islamic::weekday weekday() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday_last& x, const weekday_last& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday_last& x, const weekday_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_last& wdl);
+
+// year_month
+
+class year_month
+{
+    islamic::year  y_;
+    islamic::month m_;
+
+public:
+    CONSTCD11 year_month(const islamic::year& y, const islamic::month& m) NOEXCEPT;
+
+    CONSTCD11 islamic::year  year()  const NOEXCEPT;
+    CONSTCD11 islamic::month month() const NOEXCEPT;
+
+    CONSTCD14 year_month& operator+=(const months& dm) NOEXCEPT;
+    CONSTCD14 year_month& operator-=(const months& dm) NOEXCEPT;
+    CONSTCD14 year_month& operator+=(const years& dy) NOEXCEPT;
+    CONSTCD14 year_month& operator-=(const years& dy) NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_month& x, const year_month& y) NOEXCEPT;
+
+CONSTCD14 year_month operator+(const year_month& ym, const months& dm) NOEXCEPT;
+CONSTCD14 year_month operator+(const months& dm, const year_month& ym) NOEXCEPT;
+CONSTCD14 year_month operator-(const year_month& ym, const months& dm) NOEXCEPT;
+
+CONSTCD11 months operator-(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 year_month operator+(const year_month& ym, const years& dy) NOEXCEPT;
+CONSTCD11 year_month operator+(const years& dy, const year_month& ym) NOEXCEPT;
+CONSTCD11 year_month operator-(const year_month& ym, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month& ym);
+
+// month_day
+
+class month_day
+{
+    islamic::month m_;
+    islamic::day   d_;
+
+public:
+    CONSTCD11 month_day(const islamic::month& m, const islamic::day& d) NOEXCEPT;
+
+    CONSTCD11 islamic::month month() const NOEXCEPT;
+    CONSTCD11 islamic::day   day() const NOEXCEPT;
+
+    CONSTCD14 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month_day& x, const month_day& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day& md);
+
+// month_day_last
+
+class month_day_last
+{
+    islamic::month m_;
+
+public:
+    CONSTCD11 explicit month_day_last(const islamic::month& m) NOEXCEPT;
+
+    CONSTCD11 islamic::month month() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day_last& mdl);
+
+// month_weekday
+
+class month_weekday
+{
+    islamic::month           m_;
+    islamic::weekday_indexed wdi_;
+public:
+    CONSTCD11 month_weekday(const islamic::month& m,
+                            const islamic::weekday_indexed& wdi) NOEXCEPT;
+
+    CONSTCD11 islamic::month           month()           const NOEXCEPT;
+    CONSTCD11 islamic::weekday_indexed weekday_indexed() const NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_weekday& x, const month_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_weekday& x, const month_weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday& mwd);
+
+// month_weekday_last
+
+class month_weekday_last
+{
+    islamic::month        m_;
+    islamic::weekday_last wdl_;
+
+public:
+    CONSTCD11 month_weekday_last(const islamic::month& m,
+                                 const islamic::weekday_last& wd) NOEXCEPT;
+
+    CONSTCD11 islamic::month        month()        const NOEXCEPT;
+    CONSTCD11 islamic::weekday_last weekday_last() const NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday_last& mwdl);
+
+// class year_month_day
+
+class year_month_day
+{
+    islamic::year  y_;
+    islamic::month m_;
+    islamic::day   d_;
+
+public:
+    CONSTCD11 year_month_day(const islamic::year& y, const islamic::month& m,
+                             const islamic::day& d) NOEXCEPT;
+    CONSTCD14 year_month_day(const year_month_day_last& ymdl) NOEXCEPT;
+
+    CONSTCD14 year_month_day(sys_days dp) NOEXCEPT;
+    CONSTCD14 explicit year_month_day(local_days dp) NOEXCEPT;
+
+    CONSTCD14 year_month_day& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_day& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 islamic::year  year()  const NOEXCEPT;
+    CONSTCD11 islamic::month month() const NOEXCEPT;
+    CONSTCD11 islamic::day   day()   const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD14 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD14 year_month_day from_days(days dp) NOEXCEPT;
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+
+CONSTCD14 year_month_day operator+(const year_month_day& ymd, const months& dm) NOEXCEPT;
+CONSTCD14 year_month_day operator+(const months& dm, const year_month_day& ymd) NOEXCEPT;
+CONSTCD14 year_month_day operator-(const year_month_day& ymd, const months& dm) NOEXCEPT;
+CONSTCD11 year_month_day operator+(const year_month_day& ymd, const years& dy)  NOEXCEPT;
+CONSTCD11 year_month_day operator+(const years& dy, const year_month_day& ymd)  NOEXCEPT;
+CONSTCD11 year_month_day operator-(const year_month_day& ymd, const years& dy)  NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day& ymd);
+
+// year_month_day_last
+
+class year_month_day_last
+{
+    islamic::year           y_;
+    islamic::month_day_last mdl_;
+
+public:
+    CONSTCD11 year_month_day_last(const islamic::year& y,
+                                  const islamic::month_day_last& mdl) NOEXCEPT;
+
+    CONSTCD14 year_month_day_last& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 islamic::year           year()           const NOEXCEPT;
+    CONSTCD11 islamic::month          month()          const NOEXCEPT;
+    CONSTCD11 islamic::month_day_last month_day_last() const NOEXCEPT;
+    CONSTCD14 islamic::day            day()            const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator< (const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator> (const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator<=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator>=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+
+CONSTCD14
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const months& dm) NOEXCEPT;
+
+CONSTCD14
+year_month_day_last
+operator+(const months& dm, const year_month_day_last& ymdl) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator+(const years& dy, const year_month_day_last& ymdl) NOEXCEPT;
+
+CONSTCD14
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day_last& ymdl);
+
+// year_month_weekday
+
+class year_month_weekday
+{
+    islamic::year            y_;
+    islamic::month           m_;
+    islamic::weekday_indexed wdi_;
+
+public:
+    CONSTCD11 year_month_weekday(const islamic::year& y, const islamic::month& m,
+                                   const islamic::weekday_indexed& wdi) NOEXCEPT;
+    CONSTCD14 year_month_weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD14 explicit year_month_weekday(const local_days& dp) NOEXCEPT;
+
+    CONSTCD14 year_month_weekday& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 islamic::year year() const NOEXCEPT;
+    CONSTCD11 islamic::month month() const NOEXCEPT;
+    CONSTCD11 islamic::weekday weekday() const NOEXCEPT;
+    CONSTCD11 unsigned index() const NOEXCEPT;
+    CONSTCD11 islamic::weekday_indexed weekday_indexed() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD14 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD14 year_month_weekday from_days(days dp) NOEXCEPT;
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const months& dm) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday
+operator+(const months& dm, const year_month_weekday& ymwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator+(const years& dy, const year_month_weekday& ymwd) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday& ymwdi);
+
+// year_month_weekday_last
+
+class year_month_weekday_last
+{
+    islamic::year y_;
+    islamic::month m_;
+    islamic::weekday_last wdl_;
+
+public:
+    CONSTCD11 year_month_weekday_last(const islamic::year& y, const islamic::month& m,
+                                      const islamic::weekday_last& wdl) NOEXCEPT;
+
+    CONSTCD14 year_month_weekday_last& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator+=(const years& y) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 islamic::year year() const NOEXCEPT;
+    CONSTCD11 islamic::month month() const NOEXCEPT;
+    CONSTCD11 islamic::weekday weekday() const NOEXCEPT;
+    CONSTCD11 islamic::weekday_last weekday_last() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+private:
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11
+bool
+operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT;
+
+CONSTCD11
+bool
+operator!=(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday_last
+operator+(const months& dm, const year_month_weekday_last& ymwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator+(const years& dy, const year_month_weekday_last& ymwdl) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday_last& ymwdl);
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+inline namespace literals
+{
+
+CONSTCD11 islamic::day  operator "" _d(unsigned long long d) NOEXCEPT;
+CONSTCD11 islamic::year operator "" _y(unsigned long long y) NOEXCEPT;
+
+}  // inline namespace literals
+#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+//----------------+
+// Implementation |
+//----------------+
+
+// day
+
+CONSTCD11 inline day::day(unsigned d) NOEXCEPT : d_(static_cast<unsigned char>(d)) {}
+CONSTCD14 inline day& day::operator++() NOEXCEPT {++d_; return *this;}
+CONSTCD14 inline day day::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline day& day::operator--() NOEXCEPT {--d_; return *this;}
+CONSTCD14 inline day day::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+CONSTCD14 inline day& day::operator+=(const days& d) NOEXCEPT {*this = *this + d; return *this;}
+CONSTCD14 inline day& day::operator-=(const days& d) NOEXCEPT {*this = *this - d; return *this;}
+CONSTCD11 inline day::operator unsigned() const NOEXCEPT {return d_;}
+CONSTCD11 inline bool day::ok() const NOEXCEPT {return 1 <= d_ && d_ <= 30;}
+
+CONSTCD11
+inline
+bool
+operator==(const day& x, const day& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const day& x, const day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const day& x, const day& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const day& x, const day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const day& x, const day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const day& x, const day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+days
+operator-(const day& x, const day& y) NOEXCEPT
+{
+    return days{static_cast<days::rep>(static_cast<unsigned>(x)
+                                     - static_cast<unsigned>(y))};
+}
+
+CONSTCD11
+inline
+day
+operator+(const day& x, const days& y) NOEXCEPT
+{
+    return day{static_cast<unsigned>(x) + static_cast<unsigned>(y.count())};
+}
+
+CONSTCD11
+inline
+day
+operator+(const days& x, const day& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+day
+operator-(const day& x, const days& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const day& d)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::right);
+    os.width(2);
+    os << static_cast<unsigned>(d);
+    return os;
+}
+
+// month
+
+CONSTCD11 inline month::month(unsigned m) NOEXCEPT : m_(static_cast<decltype(m_)>(m)) {}
+CONSTCD14 inline month& month::operator++() NOEXCEPT {if (++m_ == 13) m_ = 1; return *this;}
+CONSTCD14 inline month month::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline month& month::operator--() NOEXCEPT {if (--m_ == 0) m_ = 12; return *this;}
+CONSTCD14 inline month month::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+CONSTCD14
+inline
+month&
+month::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+month&
+month::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD11 inline month::operator unsigned() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool month::ok() const NOEXCEPT {return 1 <= m_ && m_ <= 12;}
+
+CONSTCD11
+inline
+bool
+operator==(const month& x, const month& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month& x, const month& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month& x, const month& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month& x, const month& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month& x, const month& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month& x, const month& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD14
+inline
+months
+operator-(const month& x, const month& y) NOEXCEPT
+{
+    auto const d = static_cast<unsigned>(x) - static_cast<unsigned>(y);
+    return months(d <= 11 ? d : d + 12);
+}
+
+CONSTCD14
+inline
+month
+operator+(const month& x, const months& y) NOEXCEPT
+{
+    auto const mu = static_cast<long long>(static_cast<unsigned>(x)) - 1 + y.count();
+    auto const yr = (mu >= 0 ? mu : mu-11) / 12;
+    return month{static_cast<unsigned>(mu - yr * 12 + 1)};
+}
+
+CONSTCD14
+inline
+month
+operator+(const months& x, const month& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD14
+inline
+month
+operator-(const month& x, const months& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month& m)
+{
+    switch (static_cast<unsigned>(m))
+    {
+    case 1:
+        os << "Muharram";
+        break;
+    case 2:
+        os << "Safar";
+        break;
+    case 3:
+        os << "Rabi' al-awwal";
+        break;
+    case 4:
+        os << "Rabi' al-thani";
+        break;
+    case 5:
+        os << "Jumada al-awwal";
+        break;
+    case 6:
+        os << "Jumada al-Thani";
+        break;
+    case 7:
+        os << "Rajab";
+        break;
+    case 8:
+        os << "Sha'ban";
+        break;
+    case 9:
+        os << "Ramadan";
+        break;
+    case 10:
+        os << "Shawwal";
+        break;
+    case 11:
+        os << "Dhu al-Qi'dah";
+        break;
+    case 12:
+        os << "Dhu al-Hijjah";
+        break;
+    default:
+        os << static_cast<unsigned>(m) << " is not a valid month";
+        break;
+    }
+    return os;
+}
+
+// year
+
+CONSTCD11 inline year::year(int y) NOEXCEPT : y_(static_cast<decltype(y_)>(y)) {}
+CONSTCD14 inline year& year::operator++() NOEXCEPT {++y_; return *this;}
+CONSTCD14 inline year year::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline year& year::operator--() NOEXCEPT {--y_; return *this;}
+CONSTCD14 inline year year::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+CONSTCD14 inline year& year::operator+=(const years& y) NOEXCEPT {*this = *this + y; return *this;}
+CONSTCD14 inline year& year::operator-=(const years& y) NOEXCEPT {*this = *this - y; return *this;}
+
+CONSTCD14
+inline
+bool
+year::is_leap() const NOEXCEPT
+{
+    int y = y_ - 1;
+    const int era = (y >= 0 ? y : y-29) / 30;
+    const unsigned yoe = static_cast<unsigned>(y - era * 30);
+    switch (yoe)
+    {
+    case 1:
+    case 4:
+    case 6:
+    case 9:
+    case 12:
+    case 15:
+    case 17:
+    case 20:
+    case 23:
+    case 25:
+    case 28:
+        return true;
+    default:
+        return false;
+    }
+}
+
+CONSTCD11 inline year::operator int() const NOEXCEPT {return y_;}
+CONSTCD11 inline bool year::ok() const NOEXCEPT {return true;}
+
+CONSTCD11
+inline
+year
+year::min() NOEXCEPT
+{
+    return year{std::numeric_limits<short>::min()};
+}
+
+CONSTCD11
+inline
+year
+year::max() NOEXCEPT
+{
+    return year{std::numeric_limits<short>::max()};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) == static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) < static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year& x, const year& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year& x, const year& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+years
+operator-(const year& x, const year& y) NOEXCEPT
+{
+    return years{static_cast<int>(x) - static_cast<int>(y)};
+}
+
+CONSTCD11
+inline
+year
+operator+(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) + y.count()};
+}
+
+CONSTCD11
+inline
+year
+operator+(const years& x, const year& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+year
+operator-(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) - y.count()};
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::internal);
+    os.width(4 + (y < year{0}));
+    os << static_cast<int>(y);
+    return os;
+}
+
+// weekday
+
+CONSTCD11
+inline
+unsigned char
+weekday::weekday_from_days(int z) NOEXCEPT
+{
+    return static_cast<unsigned char>(static_cast<unsigned>(
+        z >= -4 ? (z+4) % 7 : (z+5) % 7 + 6));
+}
+
+CONSTCD11
+inline
+weekday::weekday(unsigned wd) NOEXCEPT
+    : wd_(static_cast<decltype(wd_)>(wd))
+    {}
+
+CONSTCD11
+inline
+weekday::weekday(const sys_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+CONSTCD11
+inline
+weekday::weekday(const local_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+CONSTCD14 inline weekday& weekday::operator++() NOEXCEPT {if (++wd_ == 7) wd_ = 0; return *this;}
+CONSTCD14 inline weekday weekday::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline weekday& weekday::operator--() NOEXCEPT {if (wd_-- == 0) wd_ = 6; return *this;}
+CONSTCD14 inline weekday weekday::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+CONSTCD14
+inline
+weekday&
+weekday::operator+=(const days& d) NOEXCEPT
+{
+    *this = *this + d;
+    return *this;
+}
+
+CONSTCD14
+inline
+weekday&
+weekday::operator-=(const days& d) NOEXCEPT
+{
+    *this = *this - d;
+    return *this;
+}
+
+CONSTCD11
+inline
+weekday::operator unsigned() const NOEXCEPT
+{
+    return static_cast<unsigned>(wd_);
+}
+
+CONSTCD11 inline bool weekday::ok() const NOEXCEPT {return wd_ <= 6;}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD14
+inline
+days
+operator-(const weekday& x, const weekday& y) NOEXCEPT
+{
+    auto const diff = static_cast<unsigned>(x) - static_cast<unsigned>(y);
+    return days{diff <= 6 ? diff : diff + 7};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const weekday& x, const days& y) NOEXCEPT
+{
+    auto const wdu = static_cast<long long>(static_cast<unsigned>(x)) + y.count();
+    auto const wk = (wdu >= 0 ? wdu : wdu-6) / 7;
+    return weekday{static_cast<unsigned>(wdu - wk * 7)};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const days& x, const weekday& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD14
+inline
+weekday
+operator-(const weekday& x, const days& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd)
+{
+    switch (static_cast<unsigned>(wd))
+    {
+    case 0:
+        os << "al-Aḥad";
+        break;
+    case 1:
+        os << "al-Ithnayn";
+        break;
+    case 2:
+        os << "ath-Thulāthā’";
+        break;
+    case 3:
+        os << "al-Arba‘ā’";
+        break;
+    case 4:
+        os << "al-Khamīs";
+        break;
+    case 5:
+        os << "al-Jum‘ah";
+        break;
+    case 6:
+        os << "as-Sabt";
+        break;
+    default:
+        os << static_cast<unsigned>(wd) << " is not a valid weekday";
+        break;
+    }
+    return os;
+}
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+inline namespace literals
+{
+
+CONSTCD11
+inline
+islamic::day
+operator "" _d(unsigned long long d) NOEXCEPT
+{
+    return islamic::day{static_cast<unsigned>(d)};
+}
+
+CONSTCD11
+inline
+islamic::year
+operator "" _y(unsigned long long y) NOEXCEPT
+{
+    return islamic::year(static_cast<int>(y));
+}
+#endif  // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+CONSTDATA islamic::last_spec last{};
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+}  // inline namespace literals
+#endif
+
+// weekday_indexed
+
+CONSTCD11
+inline
+weekday
+weekday_indexed::weekday() const NOEXCEPT
+{
+    return islamic::weekday{static_cast<unsigned>(wd_)};
+}
+
+CONSTCD11 inline unsigned weekday_indexed::index() const NOEXCEPT {return index_;}
+
+CONSTCD11
+inline
+bool
+weekday_indexed::ok() const NOEXCEPT
+{
+    return weekday().ok() && 1 <= index_ && index_ <= 5;
+}
+
+CONSTCD11
+inline
+weekday_indexed::weekday_indexed(const islamic::weekday& wd, unsigned index) NOEXCEPT
+    : wd_(static_cast<decltype(wd_)>(static_cast<unsigned>(wd)))
+    , index_(static_cast<decltype(index_)>(index))
+    {}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_indexed& wdi)
+{
+    return os << wdi.weekday() << '[' << wdi.index() << ']';
+}
+
+CONSTCD11
+inline
+weekday_indexed
+weekday::operator[](unsigned index) const NOEXCEPT
+{
+    return {*this, index};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT
+{
+    return x.weekday() == y.weekday() && x.index() == y.index();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+// weekday_last
+
+CONSTCD11 inline islamic::weekday weekday_last::weekday() const NOEXCEPT {return wd_;}
+CONSTCD11 inline bool weekday_last::ok() const NOEXCEPT {return wd_.ok();}
+CONSTCD11 inline weekday_last::weekday_last(const islamic::weekday& wd) NOEXCEPT : wd_(wd) {}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday_last& x, const weekday_last& y) NOEXCEPT
+{
+    return x.weekday() == y.weekday();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday_last& x, const weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_last& wdl)
+{
+    return os << wdl.weekday() << "[last]";
+}
+
+CONSTCD11
+inline
+weekday_last
+weekday::operator[](last_spec) const NOEXCEPT
+{
+    return weekday_last{*this};
+}
+
+// year_month
+
+CONSTCD11
+inline
+year_month::year_month(const islamic::year& y, const islamic::month& m) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    {}
+
+CONSTCD11 inline year year_month::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool year_month::ok() const NOEXCEPT {return y_.ok() && m_.ok();}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator+=(const months& dm) NOEXCEPT
+{
+    *this = *this + dm;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator-=(const months& dm) NOEXCEPT
+{
+    *this = *this - dm;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator+=(const years& dy) NOEXCEPT
+{
+    *this = *this + dy;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator-=(const years& dy) NOEXCEPT
+{
+    *this = *this - dy;
+    return *this;
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month() < y.month()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD14
+inline
+year_month
+operator+(const year_month& ym, const months& dm) NOEXCEPT
+{
+    auto dmi = static_cast<int>(static_cast<unsigned>(ym.month())) - 1 + dm.count();
+    auto dy = (dmi >= 0 ? dmi : dmi-11) / 12;
+    dmi = dmi - dy * 12 + 1;
+    return (ym.year() + years(dy)) / month(static_cast<unsigned>(dmi));
+}
+
+CONSTCD14
+inline
+year_month
+operator+(const months& dm, const year_month& ym) NOEXCEPT
+{
+    return ym + dm;
+}
+
+CONSTCD14
+inline
+year_month
+operator-(const year_month& ym, const months& dm) NOEXCEPT
+{
+    return ym + -dm;
+}
+
+CONSTCD11
+inline
+months
+operator-(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return (x.year() - y.year()) +
+            months(static_cast<unsigned>(x.month()) - static_cast<unsigned>(y.month()));
+}
+
+CONSTCD11
+inline
+year_month
+operator+(const year_month& ym, const years& dy) NOEXCEPT
+{
+    return (ym.year() + dy) / ym.month();
+}
+
+CONSTCD11
+inline
+year_month
+operator+(const years& dy, const year_month& ym) NOEXCEPT
+{
+    return ym + dy;
+}
+
+CONSTCD11
+inline
+year_month
+operator-(const year_month& ym, const years& dy) NOEXCEPT
+{
+    return ym + -dy;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month& ym)
+{
+    return os << ym.year() << '/' << ym.month();
+}
+
+// month_day
+
+CONSTCD11
+inline
+month_day::month_day(const islamic::month& m, const islamic::day& d) NOEXCEPT
+    : m_(m)
+    , d_(d)
+    {}
+
+CONSTCD11 inline islamic::month month_day::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline islamic::day month_day::day() const NOEXCEPT {return d_;}
+
+CONSTCD14
+inline
+bool
+month_day::ok() const NOEXCEPT
+{
+    CONSTDATA islamic::day d[] =
+        {30_d, 29_d, 30_d, 29_d, 30_d, 29_d, 30_d, 29_d, 30_d, 29_d, 30_d, 30_d};
+    return m_.ok() && 1_d <= d_ && d_ <= d[static_cast<unsigned>(m_)-1];
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.day() == y.day();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return x.month() < y.month() ? true
+        : (x.month() > y.month() ? false
+        : (x.day() < y.day()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day& md)
+{
+    return os << md.month() << '/' << md.day();
+}
+
+// month_day_last
+
+CONSTCD11 inline month month_day_last::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool month_day_last::ok() const NOEXCEPT {return m_.ok();}
+CONSTCD11 inline month_day_last::month_day_last(const islamic::month& m) NOEXCEPT : m_(m) {}
+
+CONSTCD11
+inline
+bool
+operator==(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return x.month() == y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return x.month() < y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day_last& mdl)
+{
+    return os << mdl.month() << "/last";
+}
+
+// month_weekday
+
+CONSTCD11
+inline
+month_weekday::month_weekday(const islamic::month& m,
+                             const islamic::weekday_indexed& wdi) NOEXCEPT
+    : m_(m)
+    , wdi_(wdi)
+    {}
+
+CONSTCD11 inline month month_weekday::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday_indexed
+month_weekday::weekday_indexed() const NOEXCEPT
+{
+    return wdi_;
+}
+
+CONSTCD11
+inline
+bool
+month_weekday::ok() const NOEXCEPT
+{
+    return m_.ok() && wdi_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_weekday& x, const month_weekday& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.weekday_indexed() == y.weekday_indexed();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_weekday& x, const month_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday& mwd)
+{
+    return os << mwd.month() << '/' << mwd.weekday_indexed();
+}
+
+// month_weekday_last
+
+CONSTCD11
+inline
+month_weekday_last::month_weekday_last(const islamic::month& m,
+                                       const islamic::weekday_last& wdl) NOEXCEPT
+    : m_(m)
+    , wdl_(wdl)
+    {}
+
+CONSTCD11 inline month month_weekday_last::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday_last
+month_weekday_last::weekday_last() const NOEXCEPT
+{
+    return wdl_;
+}
+
+CONSTCD11
+inline
+bool
+month_weekday_last::ok() const NOEXCEPT
+{
+    return m_.ok() && wdl_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.weekday_last() == y.weekday_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday_last& mwdl)
+{
+    return os << mwdl.month() << '/' << mwdl.weekday_last();
+}
+
+// year_month_day_last
+
+CONSTCD11
+inline
+year_month_day_last::year_month_day_last(const islamic::year& y,
+                                         const islamic::month_day_last& mdl) NOEXCEPT
+    : y_(y)
+    , mdl_(mdl)
+    {}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_day_last::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_day_last::month() const NOEXCEPT {return mdl_.month();}
+
+CONSTCD11
+inline
+month_day_last
+year_month_day_last::month_day_last() const NOEXCEPT
+{
+    return mdl_;
+}
+
+CONSTCD14
+inline
+day
+year_month_day_last::day() const NOEXCEPT
+{
+    CONSTDATA islamic::day d[] =
+        {30_d, 29_d, 30_d, 29_d, 30_d, 29_d, 30_d, 29_d, 30_d, 29_d, 30_d, 29_d};
+    return month() != islamic::month(12) || !y_.is_leap() ?
+               d[static_cast<unsigned>(month())-1] : 30_d;
+}
+
+CONSTCD14
+inline
+year_month_day_last::operator sys_days() const NOEXCEPT
+{
+    return sys_days(year()/month()/day());
+}
+
+CONSTCD14
+inline
+year_month_day_last::operator local_days() const NOEXCEPT
+{
+    return local_days(year()/month()/day());
+}
+
+CONSTCD11
+inline
+bool
+year_month_day_last::ok() const NOEXCEPT
+{
+    return y_.ok() && mdl_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month_day_last() == y.month_day_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month_day_last() < y.month_day_last()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day_last& ymdl)
+{
+    return os << ymdl.year() << '/' << ymdl.month_day_last();
+}
+
+CONSTCD14
+inline
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const months& dm) NOEXCEPT
+{
+    return (ymdl.year() / ymdl.month() + dm) / last;
+}
+
+CONSTCD14
+inline
+year_month_day_last
+operator+(const months& dm, const year_month_day_last& ymdl) NOEXCEPT
+{
+    return ymdl + dm;
+}
+
+CONSTCD14
+inline
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const months& dm) NOEXCEPT
+{
+    return ymdl + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const years& dy) NOEXCEPT
+{
+    return {ymdl.year()+dy, ymdl.month_day_last()};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator+(const years& dy, const year_month_day_last& ymdl) NOEXCEPT
+{
+    return ymdl + dy;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const years& dy) NOEXCEPT
+{
+    return ymdl + (-dy);
+}
+
+// year_month_day
+
+CONSTCD11
+inline
+year_month_day::year_month_day(const islamic::year& y, const islamic::month& m,
+                               const islamic::day& d) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , d_(d)
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(const year_month_day_last& ymdl) NOEXCEPT
+    : y_(ymdl.year())
+    , m_(ymdl.month())
+    , d_(ymdl.day())
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(sys_days dp) NOEXCEPT
+    : year_month_day(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(local_days dp) NOEXCEPT
+    : year_month_day(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD11 inline year year_month_day::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_day::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline day year_month_day::day() const NOEXCEPT {return d_;}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD14
+inline
+days
+year_month_day::to_days() const NOEXCEPT
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18,
+             "This algorithm has not been ported to a 16 bit unsigned integer");
+    static_assert(std::numeric_limits<int>::digits >= 20,
+             "This algorithm has not been ported to a 16 bit signed integer");
+    auto const y = static_cast<int>(y_) - 1;
+    auto const m = static_cast<unsigned>(m_);
+    auto const d = static_cast<unsigned>(d_);
+    auto const era = (y >= 0 ? y : y-29) / 30;
+    auto const yoe = static_cast<unsigned>(y - era * 30);      // [0, 29]
+    auto const doy = 29*(m-1) + m/2 + d-1;                     // [0, 354]
+    auto const doe = yoe * 354 + (11*(yoe+1)+3)/30 + doy;      // [0, 10630]
+    return days{era * 10631 + static_cast<int>(doe) - 492148};
+}
+
+CONSTCD14
+inline
+year_month_day::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_day::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD14
+inline
+bool
+year_month_day::ok() const NOEXCEPT
+{
+    if (!(y_.ok() && m_.ok()))
+        return false;
+    return 1_d <= d_ && d_ <= (y_/m_/last).day();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() && x.day() == y.day();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month() < y.month() ? true
+        : (x.month() > y.month() ? false
+        : (x.day() < y.day()))));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day& ymd)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::right);
+    os << ymd.year() << '-';
+    os.width(2);
+    os << static_cast<unsigned>(ymd.month()) << '-';
+    os << ymd.day();
+    return os;
+}
+
+CONSTCD14
+inline
+year_month_day
+year_month_day::from_days(days dp) NOEXCEPT
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18,
+             "This algorithm has not been ported to a 16 bit unsigned integer");
+    static_assert(std::numeric_limits<int>::digits >= 20,
+             "This algorithm has not been ported to a 16 bit signed integer");
+    auto const z = dp.count() + 492148;
+    auto const era = (z >= 0 ? z : z - 10630) / 10631;
+    auto const doe = static_cast<unsigned>(z - era * 10631);         // [0, 10630]
+    auto const yoe = (30*doe + 10646)/10631 - 1;                     // [0, 29]
+    auto const y = static_cast<sys_days::rep>(yoe) + era * 30 + 1;
+    auto const doy = doe - (yoe * 354 + (11*(yoe+1)+3)/30);          // [0, 354]
+    auto const m = (11*doy + 330) / 325;                             // [1, 12]
+    auto const d = doy - (29*(m-1) + m/2) + 1;                       // [1, 30]
+    return year_month_day{islamic::year{y}, islamic::month(m), islamic::day(d)};
+}
+
+CONSTCD14
+inline
+year_month_day
+operator+(const year_month_day& ymd, const months& dm) NOEXCEPT
+{
+    return (ymd.year() / ymd.month() + dm) / ymd.day();
+}
+
+CONSTCD14
+inline
+year_month_day
+operator+(const months& dm, const year_month_day& ymd) NOEXCEPT
+{
+    return ymd + dm;
+}
+
+CONSTCD14
+inline
+year_month_day
+operator-(const year_month_day& ymd, const months& dm) NOEXCEPT
+{
+    return ymd + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_day
+operator+(const year_month_day& ymd, const years& dy) NOEXCEPT
+{
+    return (ymd.year() + dy) / ymd.month() / ymd.day();
+}
+
+CONSTCD11
+inline
+year_month_day
+operator+(const years& dy, const year_month_day& ymd) NOEXCEPT
+{
+    return ymd + dy;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator-(const year_month_day& ymd, const years& dy) NOEXCEPT
+{
+    return ymd + (-dy);
+}
+
+// year_month_weekday
+
+CONSTCD11
+inline
+year_month_weekday::year_month_weekday(const islamic::year& y, const islamic::month& m,
+                                       const islamic::weekday_indexed& wdi)
+        NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , wdi_(wdi)
+    {}
+
+CONSTCD14
+inline
+year_month_weekday::year_month_weekday(const sys_days& dp) NOEXCEPT
+    : year_month_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_weekday::year_month_weekday(const local_days& dp) NOEXCEPT
+    : year_month_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_weekday::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_weekday::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday
+year_month_weekday::weekday() const NOEXCEPT
+{
+    return wdi_.weekday();
+}
+
+CONSTCD11
+inline
+unsigned
+year_month_weekday::index() const NOEXCEPT
+{
+    return wdi_.index();
+}
+
+CONSTCD11
+inline
+weekday_indexed
+year_month_weekday::weekday_indexed() const NOEXCEPT
+{
+    return wdi_;
+}
+
+CONSTCD14
+inline
+year_month_weekday::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_weekday::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD14
+inline
+bool
+year_month_weekday::ok() const NOEXCEPT
+{
+    if (!y_.ok() || !m_.ok() || !wdi_.weekday().ok() || wdi_.index() < 1)
+        return false;
+    if (wdi_.index() <= 4)
+        return true;
+    auto d2 = wdi_.weekday() - islamic::weekday(y_/m_/1) + days((wdi_.index()-1)*7 + 1);
+    return static_cast<unsigned>(d2.count()) <= static_cast<unsigned>((y_/m_/last).day());
+}
+
+CONSTCD14
+inline
+year_month_weekday
+year_month_weekday::from_days(days d) NOEXCEPT
+{
+    sys_days dp{d};
+    auto const wd = islamic::weekday(dp);
+    auto const ymd = year_month_day(dp);
+    return {ymd.year(), ymd.month(), wd[(static_cast<unsigned>(ymd.day())-1)/7+1]};
+}
+
+CONSTCD14
+inline
+days
+year_month_weekday::to_days() const NOEXCEPT
+{
+    auto d = sys_days(y_/m_/1);
+    return (d + (wdi_.weekday() - islamic::weekday(d) + days{(wdi_.index()-1)*7})
+           ).time_since_epoch();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() &&
+           x.weekday_indexed() == y.weekday_indexed();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday& ymwdi)
+{
+    return os << ymwdi.year() << '/' << ymwdi.month()
+              << '/' << ymwdi.weekday_indexed();
+}
+
+CONSTCD14
+inline
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const months& dm) NOEXCEPT
+{
+    return (ymwd.year() / ymwd.month() + dm) / ymwd.weekday_indexed();
+}
+
+CONSTCD14
+inline
+year_month_weekday
+operator+(const months& dm, const year_month_weekday& ymwd) NOEXCEPT
+{
+    return ymwd + dm;
+}
+
+CONSTCD14
+inline
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const months& dm) NOEXCEPT
+{
+    return ymwd + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const years& dy) NOEXCEPT
+{
+    return {ymwd.year()+dy, ymwd.month(), ymwd.weekday_indexed()};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator+(const years& dy, const year_month_weekday& ymwd) NOEXCEPT
+{
+    return ymwd + dy;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const years& dy) NOEXCEPT
+{
+    return ymwd + (-dy);
+}
+
+// year_month_weekday_last
+
+CONSTCD11
+inline
+year_month_weekday_last::year_month_weekday_last(const islamic::year& y,
+                                                 const islamic::month& m,
+                                                 const islamic::weekday_last& wdl) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , wdl_(wdl)
+    {}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_weekday_last::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_weekday_last::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday
+year_month_weekday_last::weekday() const NOEXCEPT
+{
+    return wdl_.weekday();
+}
+
+CONSTCD11
+inline
+weekday_last
+year_month_weekday_last::weekday_last() const NOEXCEPT
+{
+    return wdl_;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_weekday_last::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD11
+inline
+bool
+year_month_weekday_last::ok() const NOEXCEPT
+{
+    return y_.ok() && m_.ok() && wdl_.ok();
+}
+
+CONSTCD14
+inline
+days
+year_month_weekday_last::to_days() const NOEXCEPT
+{
+    auto const d = sys_days(y_/m_/last);
+    return (d - (islamic::weekday{d} - wdl_.weekday())).time_since_epoch();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() &&
+           x.weekday_last() == y.weekday_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday_last& ymwdl)
+{
+    return os << ymwdl.year() << '/' << ymwdl.month() << '/' << ymwdl.weekday_last();
+}
+
+CONSTCD14
+inline
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT
+{
+    return (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last();
+}
+
+CONSTCD14
+inline
+year_month_weekday_last
+operator+(const months& dm, const year_month_weekday_last& ymwdl) NOEXCEPT
+{
+    return ymwdl + dm;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT
+{
+    return ymwdl + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT
+{
+    return {ymwdl.year()+dy, ymwdl.month(), ymwdl.weekday_last()};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator+(const years& dy, const year_month_weekday_last& ymwdl) NOEXCEPT
+{
+    return ymwdl + dy;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT
+{
+    return ymwdl + (-dy);
+}
+
+// year_month from operator/()
+
+CONSTCD11
+inline
+year_month
+operator/(const year& y, const month& m) NOEXCEPT
+{
+    return {y, m};
+}
+
+CONSTCD11
+inline
+year_month
+operator/(const year& y, int   m) NOEXCEPT
+{
+    return y / month(static_cast<unsigned>(m));
+}
+
+// month_day from operator/()
+
+CONSTCD11
+inline
+month_day
+operator/(const month& m, const day& d) NOEXCEPT
+{
+    return {m, d};
+}
+
+CONSTCD11
+inline
+month_day
+operator/(const day& d, const month& m) NOEXCEPT
+{
+    return m / d;
+}
+
+CONSTCD11
+inline
+month_day
+operator/(const month& m, int d) NOEXCEPT
+{
+    return m / day(static_cast<unsigned>(d));
+}
+
+CONSTCD11
+inline
+month_day
+operator/(int m, const day& d) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / d;
+}
+
+CONSTCD11 inline month_day operator/(const day& d, int m) NOEXCEPT {return m / d;}
+
+// month_day_last from operator/()
+
+CONSTCD11
+inline
+month_day_last
+operator/(const month& m, last_spec) NOEXCEPT
+{
+    return month_day_last{m};
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(last_spec, const month& m) NOEXCEPT
+{
+    return m/last;
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(int m, last_spec) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m))/last;
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(last_spec, int m) NOEXCEPT
+{
+    return m/last;
+}
+
+// month_weekday from operator/()
+
+CONSTCD11
+inline
+month_weekday
+operator/(const month& m, const weekday_indexed& wdi) NOEXCEPT
+{
+    return {m, wdi};
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(const weekday_indexed& wdi, const month& m) NOEXCEPT
+{
+    return m / wdi;
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(int m, const weekday_indexed& wdi) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / wdi;
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(const weekday_indexed& wdi, int m) NOEXCEPT
+{
+    return m / wdi;
+}
+
+// month_weekday_last from operator/()
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const month& m, const weekday_last& wdl) NOEXCEPT
+{
+    return {m, wdl};
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const weekday_last& wdl, const month& m) NOEXCEPT
+{
+    return m / wdl;
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(int m, const weekday_last& wdl) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / wdl;
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const weekday_last& wdl, int m) NOEXCEPT
+{
+    return m / wdl;
+}
+
+// year_month_day from operator/()
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year_month& ym, const day& d) NOEXCEPT
+{
+    return {ym.year(), ym.month(), d};
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year_month& ym, int d)  NOEXCEPT
+{
+    return ym / day(static_cast<unsigned>(d));
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year& y, const month_day& md) NOEXCEPT
+{
+    return y / md.month() / md.day();
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(int y, const month_day& md) NOEXCEPT
+{
+    return year(y) / md;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const month_day& md, const year& y)  NOEXCEPT
+{
+    return y / md;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const month_day& md, int y) NOEXCEPT
+{
+    return year(y) / md;
+}
+
+// year_month_day_last from operator/()
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const year_month& ym, last_spec) NOEXCEPT
+{
+    return {ym.year(), month_day_last{ym.month()}};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const year& y, const month_day_last& mdl) NOEXCEPT
+{
+    return {y, mdl};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(int y, const month_day_last& mdl) NOEXCEPT
+{
+    return year(y) / mdl;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const month_day_last& mdl, const year& y) NOEXCEPT
+{
+    return y / mdl;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const month_day_last& mdl, int y) NOEXCEPT
+{
+    return year(y) / mdl;
+}
+
+// year_month_weekday from operator/()
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const year_month& ym, const weekday_indexed& wdi) NOEXCEPT
+{
+    return {ym.year(), ym.month(), wdi};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const year& y, const month_weekday& mwd) NOEXCEPT
+{
+    return {y, mwd.month(), mwd.weekday_indexed()};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(int y, const month_weekday& mwd) NOEXCEPT
+{
+    return year(y) / mwd;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const month_weekday& mwd, const year& y) NOEXCEPT
+{
+    return y / mwd;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const month_weekday& mwd, int y) NOEXCEPT
+{
+    return year(y) / mwd;
+}
+
+// year_month_weekday_last from operator/()
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const year_month& ym, const weekday_last& wdl) NOEXCEPT
+{
+    return {ym.year(), ym.month(), wdl};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const year& y, const month_weekday_last& mwdl) NOEXCEPT
+{
+    return {y, mwdl.month(), mwdl.weekday_last()};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(int y, const month_weekday_last& mwdl) NOEXCEPT
+{
+    return year(y) / mwdl;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, const year& y) NOEXCEPT
+{
+    return y / mwdl;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, int y) NOEXCEPT
+{
+    return year(y) / mwdl;
+}
+
+}  // namespace islamic
+
+#endif  // ISLAMIC_H
diff --git a/src/libs/date/includes/date/iso_week.h b/src/libs/date/includes/date/iso_week.h
new file mode 100644
index 00000000..4a0a4a9b
--- /dev/null
+++ b/src/libs/date/includes/date/iso_week.h
@@ -0,0 +1,1751 @@
+#ifndef ISO_WEEK_H
+#define ISO_WEEK_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2015, 2016, 2017 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#include "date.h"
+
+#include <climits>
+
+namespace iso_week
+{
+
+// y/wn/wd
+// wn/wd/y
+// wd/wn/y
+
+using days = date::days;
+using weeks = date::weeks;
+using years = date::years;
+
+// time_point
+
+using sys_days = date::sys_days;
+using local_days = date::local_days;
+
+// types
+
+struct last_week
+{
+    explicit last_week() = default;
+};
+
+class weekday;
+class weeknum;
+class year;
+
+class year_weeknum;
+class year_lastweek;
+class weeknum_weekday;
+class lastweek_weekday;
+
+class year_weeknum_weekday;
+class year_lastweek_weekday;
+
+// date composition operators
+
+CONSTCD11 year_weeknum operator/(const year& y, const weeknum& wn) NOEXCEPT;
+CONSTCD11 year_weeknum operator/(const year& y, int            wn) NOEXCEPT;
+
+CONSTCD11 year_lastweek operator/(const year& y, last_week      wn) NOEXCEPT;
+
+CONSTCD11 weeknum_weekday operator/(const weeknum& wn, const weekday& wd) NOEXCEPT;
+CONSTCD11 weeknum_weekday operator/(const weeknum& wn, int            wd) NOEXCEPT;
+CONSTCD11 weeknum_weekday operator/(const weekday& wd, const weeknum& wn) NOEXCEPT;
+CONSTCD11 weeknum_weekday operator/(const weekday& wd, int            wn) NOEXCEPT;
+
+CONSTCD11 lastweek_weekday operator/(const last_week& wn, const weekday& wd) NOEXCEPT;
+CONSTCD11 lastweek_weekday operator/(const last_week& wn, int            wd) NOEXCEPT;
+CONSTCD11 lastweek_weekday operator/(const weekday& wd, const last_week& wn) NOEXCEPT;
+
+CONSTCD11 year_weeknum_weekday operator/(const year_weeknum& ywn, const weekday& wd) NOEXCEPT;
+CONSTCD11 year_weeknum_weekday operator/(const year_weeknum& ywn, int            wd) NOEXCEPT;
+CONSTCD11 year_weeknum_weekday operator/(const weeknum_weekday& wnwd, const year& y) NOEXCEPT;
+CONSTCD11 year_weeknum_weekday operator/(const weeknum_weekday& wnwd, int         y) NOEXCEPT;
+
+CONSTCD11 year_lastweek_weekday operator/(const year_lastweek& ylw, const weekday& wd) NOEXCEPT;
+CONSTCD11 year_lastweek_weekday operator/(const year_lastweek& ylw, int            wd) NOEXCEPT;
+
+CONSTCD11 year_lastweek_weekday operator/(const lastweek_weekday& lwwd, const year& y) NOEXCEPT;
+CONSTCD11 year_lastweek_weekday operator/(const lastweek_weekday& lwwd, int         y) NOEXCEPT;
+
+// weekday
+
+class weekday
+{
+    unsigned char wd_;
+public:
+    explicit CONSTCD11 weekday(unsigned wd) NOEXCEPT;
+    CONSTCD11 weekday(date::weekday wd) NOEXCEPT;
+    explicit weekday(int) = delete;
+    CONSTCD11 weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD11 explicit weekday(const local_days& dp) NOEXCEPT;
+
+    weekday& operator++()    NOEXCEPT;
+    weekday  operator++(int) NOEXCEPT;
+    weekday& operator--()    NOEXCEPT;
+    weekday  operator--(int) NOEXCEPT;
+
+    weekday& operator+=(const days& d) NOEXCEPT;
+    weekday& operator-=(const days& d) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 operator date::weekday() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD11 unsigned char weekday_from_days(int z) NOEXCEPT;
+    static CONSTCD11 unsigned char to_iso_encoding(unsigned char) NOEXCEPT;
+    static CONSTCD11 unsigned from_iso_encoding(unsigned) NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday& x, const weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday& x, const weekday& y) NOEXCEPT;
+
+CONSTCD14 weekday operator+(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 weekday operator+(const days&    x, const weekday& y) NOEXCEPT;
+CONSTCD14 weekday operator-(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 days    operator-(const weekday& x, const weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd);
+
+// year
+
+class year
+{
+    short y_;
+
+public:
+    explicit CONSTCD11 year(int y) NOEXCEPT;
+
+    year& operator++()    NOEXCEPT;
+    year  operator++(int) NOEXCEPT;
+    year& operator--()    NOEXCEPT;
+    year  operator--(int) NOEXCEPT;
+
+    year& operator+=(const years& y) NOEXCEPT;
+    year& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 explicit operator int() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+    static CONSTCD11 year min() NOEXCEPT;
+    static CONSTCD11 year max() NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year& x, const year& y) NOEXCEPT;
+
+CONSTCD11 year  operator+(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 year  operator+(const years& x, const year&  y) NOEXCEPT;
+CONSTCD11 year  operator-(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 years operator-(const year&  x, const year&  y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y);
+
+// weeknum
+
+class weeknum
+{
+    unsigned char wn_;
+
+public:
+    explicit CONSTCD11 weeknum(unsigned wn) NOEXCEPT;
+
+    weeknum& operator++()    NOEXCEPT;
+    weeknum  operator++(int) NOEXCEPT;
+    weeknum& operator--()    NOEXCEPT;
+    weeknum  operator--(int) NOEXCEPT;
+
+    weeknum& operator+=(const weeks& y) NOEXCEPT;
+    weeknum& operator-=(const weeks& y) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weeknum& x, const weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weeknum& x, const weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator< (const weeknum& x, const weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator> (const weeknum& x, const weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const weeknum& x, const weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const weeknum& x, const weeknum& y) NOEXCEPT;
+
+CONSTCD11 weeknum  operator+(const weeknum& x, const weeks&   y) NOEXCEPT;
+CONSTCD11 weeknum  operator+(const weeks&   x, const weeknum& y) NOEXCEPT;
+CONSTCD11 weeknum  operator-(const weeknum& x, const weeks&   y) NOEXCEPT;
+CONSTCD11 weeks    operator-(const weeknum& x, const weeknum& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weeknum& wn);
+
+// year_weeknum
+
+class year_weeknum
+{
+    iso_week::year    y_;
+    iso_week::weeknum wn_;
+
+public:
+    CONSTCD11 year_weeknum(const iso_week::year& y, const iso_week::weeknum& wn) NOEXCEPT;
+
+    CONSTCD11 iso_week::year    year()    const NOEXCEPT;
+    CONSTCD11 iso_week::weeknum weeknum() const NOEXCEPT;
+
+    year_weeknum& operator+=(const years& dy) NOEXCEPT;
+    year_weeknum& operator-=(const years& dy) NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_weeknum& x, const year_weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_weeknum& x, const year_weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_weeknum& x, const year_weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_weeknum& x, const year_weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_weeknum& x, const year_weeknum& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_weeknum& x, const year_weeknum& y) NOEXCEPT;
+
+CONSTCD11 year_weeknum operator+(const year_weeknum& ym, const years& dy) NOEXCEPT;
+CONSTCD11 year_weeknum operator+(const years& dy, const year_weeknum& ym) NOEXCEPT;
+CONSTCD11 year_weeknum operator-(const year_weeknum& ym, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_weeknum& ym);
+
+// year_lastweek
+
+class year_lastweek
+{
+    iso_week::year    y_;
+
+public:
+    CONSTCD11 explicit year_lastweek(const iso_week::year& y) NOEXCEPT;
+
+    CONSTCD11 iso_week::year    year()    const NOEXCEPT;
+    CONSTCD14 iso_week::weeknum weeknum() const NOEXCEPT;
+
+    year_lastweek& operator+=(const years& dy) NOEXCEPT;
+    year_lastweek& operator-=(const years& dy) NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_lastweek& x, const year_lastweek& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_lastweek& x, const year_lastweek& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_lastweek& x, const year_lastweek& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_lastweek& x, const year_lastweek& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_lastweek& x, const year_lastweek& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_lastweek& x, const year_lastweek& y) NOEXCEPT;
+
+CONSTCD11 year_lastweek operator+(const year_lastweek& ym, const years& dy) NOEXCEPT;
+CONSTCD11 year_lastweek operator+(const years& dy, const year_lastweek& ym) NOEXCEPT;
+CONSTCD11 year_lastweek operator-(const year_lastweek& ym, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_lastweek& ym);
+
+// weeknum_weekday
+
+class weeknum_weekday
+{
+    iso_week::weeknum wn_;
+    iso_week::weekday wd_;
+
+public:
+    CONSTCD11 weeknum_weekday(const iso_week::weeknum& wn,
+                              const iso_week::weekday& wd) NOEXCEPT;
+
+    CONSTCD11 iso_week::weeknum weeknum() const NOEXCEPT;
+    CONSTCD11 iso_week::weekday weekday() const NOEXCEPT;
+
+    CONSTCD14 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator< (const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator> (const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weeknum_weekday& md);
+
+// lastweek_weekday
+
+class lastweek_weekday
+{
+    iso_week::weekday wd_;
+
+public:
+    CONSTCD11 explicit lastweek_weekday(const iso_week::weekday& wd) NOEXCEPT;
+
+    CONSTCD11 iso_week::weekday weekday() const NOEXCEPT;
+
+    CONSTCD14 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator< (const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator> (const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const lastweek_weekday& md);
+
+// year_lastweek_weekday
+
+class year_lastweek_weekday
+{
+    iso_week::year    y_;
+    iso_week::weekday wd_;
+
+public:
+    CONSTCD11 year_lastweek_weekday(const iso_week::year& y,
+                                    const iso_week::weekday& wd) NOEXCEPT;
+
+    year_lastweek_weekday& operator+=(const years& y) NOEXCEPT;
+    year_lastweek_weekday& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 iso_week::year    year()    const NOEXCEPT;
+    CONSTCD14 iso_week::weeknum weeknum() const NOEXCEPT;
+    CONSTCD11 iso_week::weekday weekday() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT;
+
+CONSTCD11 year_lastweek_weekday operator+(const year_lastweek_weekday& ywnwd, const years& y) NOEXCEPT;
+CONSTCD11 year_lastweek_weekday operator+(const years& y, const year_lastweek_weekday& ywnwd) NOEXCEPT;
+CONSTCD11 year_lastweek_weekday operator-(const year_lastweek_weekday& ywnwd, const years& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_lastweek_weekday& ywnwd);
+
+// class year_weeknum_weekday
+
+class year_weeknum_weekday
+{
+    iso_week::year    y_;
+    iso_week::weeknum wn_;
+    iso_week::weekday wd_;
+
+public:
+    CONSTCD11 year_weeknum_weekday(const iso_week::year& y, const iso_week::weeknum& wn,
+                                   const iso_week::weekday& wd) NOEXCEPT;
+    CONSTCD14 year_weeknum_weekday(const year_lastweek_weekday& ylwwd) NOEXCEPT;
+    CONSTCD14 year_weeknum_weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD14 explicit year_weeknum_weekday(const local_days& dp) NOEXCEPT;
+
+    year_weeknum_weekday& operator+=(const years& y) NOEXCEPT;
+    year_weeknum_weekday& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 iso_week::year    year()    const NOEXCEPT;
+    CONSTCD11 iso_week::weeknum weeknum() const NOEXCEPT;
+    CONSTCD11 iso_week::weekday weekday() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD14 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD14 year_weeknum_weekday from_days(days dp) NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT;
+
+CONSTCD11 year_weeknum_weekday operator+(const year_weeknum_weekday& ywnwd, const years& y) NOEXCEPT;
+CONSTCD11 year_weeknum_weekday operator+(const years& y, const year_weeknum_weekday& ywnwd) NOEXCEPT;
+CONSTCD11 year_weeknum_weekday operator-(const year_weeknum_weekday& ywnwd, const years& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_weeknum_weekday& ywnwd);
+
+//----------------+
+// Implementation |
+//----------------+
+
+// weekday
+
+CONSTCD11
+inline
+unsigned char
+weekday::to_iso_encoding(unsigned char z) NOEXCEPT
+{
+    return z != 0 ? z : (unsigned char)7;
+}
+
+CONSTCD11
+inline
+unsigned
+weekday::from_iso_encoding(unsigned z) NOEXCEPT
+{
+    return z != 7 ? z : 0u;
+}
+
+CONSTCD11
+inline
+unsigned char
+weekday::weekday_from_days(int z) NOEXCEPT
+{
+    return to_iso_encoding(static_cast<unsigned char>(static_cast<unsigned>(
+        z >= -4 ? (z+4) % 7 : (z+5) % 7 + 6)));
+}
+
+CONSTCD11
+inline
+weekday::weekday(unsigned wd) NOEXCEPT
+    : wd_(static_cast<decltype(wd_)>(wd))
+    {}
+
+CONSTCD11
+inline
+weekday::weekday(date::weekday wd) NOEXCEPT
+    : wd_(wd.iso_encoding())
+    {}
+
+CONSTCD11
+inline
+weekday::weekday(const sys_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+CONSTCD11
+inline
+weekday::weekday(const local_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+inline weekday& weekday::operator++() NOEXCEPT {if (++wd_ == 8) wd_ = 1; return *this;}
+inline weekday weekday::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+inline weekday& weekday::operator--() NOEXCEPT {if (wd_-- == 1) wd_ = 7; return *this;}
+inline weekday weekday::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+inline
+weekday&
+weekday::operator+=(const days& d) NOEXCEPT
+{
+    *this = *this + d;
+    return *this;
+}
+
+inline
+weekday&
+weekday::operator-=(const days& d) NOEXCEPT
+{
+    *this = *this - d;
+    return *this;
+}
+
+CONSTCD11
+inline
+weekday::operator unsigned() const NOEXCEPT
+{
+    return wd_;
+}
+
+CONSTCD11
+inline
+weekday::operator date::weekday() const NOEXCEPT
+{
+    return date::weekday{from_iso_encoding(unsigned{wd_})};
+}
+
+CONSTCD11 inline bool weekday::ok() const NOEXCEPT {return 1 <= wd_ && wd_ <= 7;}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD14
+inline
+days
+operator-(const weekday& x, const weekday& y) NOEXCEPT
+{
+    auto const diff = static_cast<unsigned>(x) - static_cast<unsigned>(y);
+    return days{diff <= 6 ? diff : diff + 7};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const weekday& x, const days& y) NOEXCEPT
+{
+    auto const wdu = static_cast<long long>(static_cast<unsigned>(x) - 1u) + y.count();
+    auto const wk = (wdu >= 0 ? wdu : wdu-6) / 7;
+    return weekday{static_cast<unsigned>(wdu - wk * 7) + 1u};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const days& x, const weekday& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD14
+inline
+weekday
+operator-(const weekday& x, const days& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd)
+{
+    switch (static_cast<unsigned>(wd))
+    {
+    case 7:
+        os << "Sun";
+        break;
+    case 1:
+        os << "Mon";
+        break;
+    case 2:
+        os << "Tue";
+        break;
+    case 3:
+        os << "Wed";
+        break;
+    case 4:
+        os << "Thu";
+        break;
+    case 5:
+        os << "Fri";
+        break;
+    case 6:
+        os << "Sat";
+        break;
+    default:
+        os << static_cast<unsigned>(wd) << " is not a valid weekday";
+        break;
+    }
+    return os;
+}
+
+// year
+
+CONSTCD11 inline year::year(int y) NOEXCEPT : y_(static_cast<decltype(y_)>(y)) {}
+inline year& year::operator++() NOEXCEPT {++y_; return *this;}
+inline year year::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+inline year& year::operator--() NOEXCEPT {--y_; return *this;}
+inline year year::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+inline year& year::operator+=(const years& y) NOEXCEPT {*this = *this + y; return *this;}
+inline year& year::operator-=(const years& y) NOEXCEPT {*this = *this - y; return *this;}
+
+CONSTCD11 inline year::operator int() const NOEXCEPT {return y_;}
+CONSTCD11 inline bool year::ok() const NOEXCEPT {return min() <= *this && *this <= max();}
+
+CONSTCD11
+inline
+year
+year::min() NOEXCEPT
+{
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    using std::chrono::hours;
+    using std::chrono::duration_cast;
+    static_assert(sizeof(seconds)*CHAR_BIT >= 41, "seconds may overflow");
+    static_assert(sizeof(hours)*CHAR_BIT >= 30, "hours may overflow");
+    return sizeof(minutes)*CHAR_BIT < 34 ?
+        year{1970} + duration_cast<years>(minutes::min()) :
+        year{std::numeric_limits<short>::min()};
+}
+
+CONSTCD11
+inline
+year
+year::max() NOEXCEPT
+{
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    using std::chrono::hours;
+    using std::chrono::duration_cast;
+    static_assert(sizeof(seconds)*CHAR_BIT >= 41, "seconds may overflow");
+    static_assert(sizeof(hours)*CHAR_BIT >= 30, "hours may overflow");
+    return sizeof(minutes)*CHAR_BIT < 34 ?
+        year{1969} + duration_cast<years>(minutes::max()) :
+        year{std::numeric_limits<short>::max()};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) == static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) < static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year& x, const year& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year& x, const year& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+years
+operator-(const year& x, const year& y) NOEXCEPT
+{
+    return years{static_cast<int>(x) - static_cast<int>(y)};
+}
+
+CONSTCD11
+inline
+year
+operator+(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) + y.count()};
+}
+
+CONSTCD11
+inline
+year
+operator+(const years& x, const year& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+year
+operator-(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) - y.count()};
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::internal);
+    os.width(4 + (y < year{0}));
+    os << static_cast<int>(y);
+    return os;
+}
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+inline namespace literals
+{
+
+CONSTCD11
+inline
+iso_week::year
+operator "" _y(unsigned long long y) NOEXCEPT
+{
+    return iso_week::year(static_cast<int>(y));
+}
+
+CONSTCD11
+inline
+iso_week::weeknum
+operator "" _w(unsigned long long wn) NOEXCEPT
+{
+    return iso_week::weeknum(static_cast<unsigned>(wn));
+}
+
+#endif  // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+CONSTDATA iso_week::last_week last{};
+
+CONSTDATA iso_week::weekday sun{7u};
+CONSTDATA iso_week::weekday mon{1u};
+CONSTDATA iso_week::weekday tue{2u};
+CONSTDATA iso_week::weekday wed{3u};
+CONSTDATA iso_week::weekday thu{4u};
+CONSTDATA iso_week::weekday fri{5u};
+CONSTDATA iso_week::weekday sat{6u};
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+}  // inline namespace literals
+#endif
+
+// weeknum
+
+CONSTCD11
+inline
+weeknum::weeknum(unsigned wn) NOEXCEPT
+    : wn_(static_cast<decltype(wn_)>(wn))
+    {}
+
+inline weeknum& weeknum::operator++() NOEXCEPT {++wn_; return *this;}
+inline weeknum weeknum::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+inline weeknum& weeknum::operator--() NOEXCEPT {--wn_; return *this;}
+inline weeknum weeknum::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+inline
+weeknum&
+weeknum::operator+=(const weeks& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+inline
+weeknum&
+weeknum::operator-=(const weeks& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline weeknum::operator unsigned() const NOEXCEPT {return wn_;}
+CONSTCD11 inline bool weeknum::ok() const NOEXCEPT {return 1 <= wn_ && wn_ <= 53;}
+
+CONSTCD11
+inline
+bool
+operator==(const weeknum& x, const weeknum& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weeknum& x, const weeknum& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const weeknum& x, const weeknum& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const weeknum& x, const weeknum& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const weeknum& x, const weeknum& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const weeknum& x, const weeknum& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+weeks
+operator-(const weeknum& x, const weeknum& y) NOEXCEPT
+{
+    return weeks{static_cast<weeks::rep>(static_cast<unsigned>(x)) -
+                 static_cast<weeks::rep>(static_cast<unsigned>(y))};
+}
+
+CONSTCD11
+inline
+weeknum
+operator+(const weeknum& x, const weeks& y) NOEXCEPT
+{
+    return weeknum{static_cast<unsigned>(x) + static_cast<unsigned>(y.count())};
+}
+
+CONSTCD11
+inline
+weeknum
+operator+(const weeks& x, const weeknum& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+weeknum
+operator-(const weeknum& x, const weeks& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weeknum& wn)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os << 'W';
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::right);
+    os.width(2);
+    os << static_cast<unsigned>(wn);
+    return os;
+}
+
+// year_weeknum
+
+CONSTCD11
+inline
+year_weeknum::year_weeknum(const iso_week::year& y, const iso_week::weeknum& wn) NOEXCEPT
+    : y_(y)
+    , wn_(wn)
+    {}
+
+CONSTCD11 inline year year_weeknum::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline weeknum year_weeknum::weeknum() const NOEXCEPT {return wn_;}
+CONSTCD11 inline bool year_weeknum::ok() const NOEXCEPT
+{
+    return y_.ok() && 1u <= static_cast<unsigned>(wn_) && wn_ <= (y_/last).weeknum();
+}
+
+inline
+year_weeknum&
+year_weeknum::operator+=(const years& dy) NOEXCEPT
+{
+    *this = *this + dy;
+    return *this;
+}
+
+inline
+year_weeknum&
+year_weeknum::operator-=(const years& dy) NOEXCEPT
+{
+    *this = *this - dy;
+    return *this;
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_weeknum& x, const year_weeknum& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.weeknum() == y.weeknum();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_weeknum& x, const year_weeknum& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_weeknum& x, const year_weeknum& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.weeknum() < y.weeknum()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_weeknum& x, const year_weeknum& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_weeknum& x, const year_weeknum& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_weeknum& x, const year_weeknum& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+year_weeknum
+operator+(const year_weeknum& ym, const years& dy) NOEXCEPT
+{
+    return (ym.year() + dy) / ym.weeknum();
+}
+
+CONSTCD11
+inline
+year_weeknum
+operator+(const years& dy, const year_weeknum& ym) NOEXCEPT
+{
+    return ym + dy;
+}
+
+CONSTCD11
+inline
+year_weeknum
+operator-(const year_weeknum& ym, const years& dy) NOEXCEPT
+{
+    return ym + -dy;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_weeknum& ywn)
+{
+    return os << ywn.year() << '-' << ywn.weeknum();
+}
+
+
+// year_lastweek
+
+CONSTCD11
+inline
+year_lastweek::year_lastweek(const iso_week::year& y) NOEXCEPT
+    : y_(y)
+    {}
+
+CONSTCD11 inline year year_lastweek::year() const NOEXCEPT {return y_;}
+
+CONSTCD14
+inline
+weeknum
+year_lastweek::weeknum() const NOEXCEPT
+{
+    const auto y = date::year{static_cast<int>(y_)};
+    const auto s0 = sys_days((y-years{1})/12/date::thu[date::last]);
+    const auto s1 = sys_days(y/12/date::thu[date::last]);
+    return iso_week::weeknum(static_cast<unsigned>(date::trunc<weeks>(s1-s0).count()));
+}
+
+CONSTCD11 inline bool year_lastweek::ok() const NOEXCEPT {return y_.ok();}
+
+inline
+year_lastweek&
+year_lastweek::operator+=(const years& dy) NOEXCEPT
+{
+    *this = *this + dy;
+    return *this;
+}
+
+inline
+year_lastweek&
+year_lastweek::operator-=(const years& dy) NOEXCEPT
+{
+    *this = *this - dy;
+    return *this;
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_lastweek& x, const year_lastweek& y) NOEXCEPT
+{
+    return x.year() == y.year();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_lastweek& x, const year_lastweek& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_lastweek& x, const year_lastweek& y) NOEXCEPT
+{
+    return x.year() < y.year();
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_lastweek& x, const year_lastweek& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_lastweek& x, const year_lastweek& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_lastweek& x, const year_lastweek& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+year_lastweek
+operator+(const year_lastweek& ym, const years& dy) NOEXCEPT
+{
+    return year_lastweek{ym.year() + dy};
+}
+
+CONSTCD11
+inline
+year_lastweek
+operator+(const years& dy, const year_lastweek& ym) NOEXCEPT
+{
+    return ym + dy;
+}
+
+CONSTCD11
+inline
+year_lastweek
+operator-(const year_lastweek& ym, const years& dy) NOEXCEPT
+{
+    return ym + -dy;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_lastweek& ywn)
+{
+    return os << ywn.year() << "-W last";
+}
+
+// weeknum_weekday
+
+CONSTCD11
+inline
+weeknum_weekday::weeknum_weekday(const iso_week::weeknum& wn,
+                                 const iso_week::weekday& wd) NOEXCEPT
+    : wn_(wn)
+    , wd_(wd)
+    {}
+
+CONSTCD11 inline weeknum weeknum_weekday::weeknum() const NOEXCEPT {return wn_;}
+CONSTCD11 inline weekday weeknum_weekday::weekday() const NOEXCEPT {return wd_;}
+
+CONSTCD14
+inline
+bool
+weeknum_weekday::ok() const NOEXCEPT
+{
+    return wn_.ok() && wd_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT
+{
+    return x.weeknum() == y.weeknum() && x.weekday() == y.weekday();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT
+{
+    return x.weeknum() < y.weeknum() ? true
+        : (x.weeknum() > y.weeknum() ? false
+        : (static_cast<unsigned>(x.weekday()) < static_cast<unsigned>(y.weekday())));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const weeknum_weekday& x, const weeknum_weekday& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weeknum_weekday& md)
+{
+    return os << md.weeknum() << '-' << md.weekday();
+}
+
+// lastweek_weekday
+
+CONSTCD11
+inline
+lastweek_weekday::lastweek_weekday(const iso_week::weekday& wd) NOEXCEPT
+    : wd_(wd)
+    {}
+
+CONSTCD11 inline weekday lastweek_weekday::weekday() const NOEXCEPT {return wd_;}
+
+CONSTCD14
+inline
+bool
+lastweek_weekday::ok() const NOEXCEPT
+{
+    return wd_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT
+{
+    return x.weekday() == y.weekday();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x.weekday()) < static_cast<unsigned>(y.weekday());
+}
+
+CONSTCD11
+inline
+bool
+operator>(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const lastweek_weekday& x, const lastweek_weekday& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const lastweek_weekday& md)
+{
+    return os << "W last-" << md.weekday();
+}
+
+// year_lastweek_weekday
+
+CONSTCD11
+inline
+year_lastweek_weekday::year_lastweek_weekday(const iso_week::year& y,
+                                             const iso_week::weekday& wd) NOEXCEPT
+    : y_(y)
+    , wd_(wd)
+    {}
+
+inline
+year_lastweek_weekday&
+year_lastweek_weekday::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+inline
+year_lastweek_weekday&
+year_lastweek_weekday::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_lastweek_weekday::year() const NOEXCEPT {return y_;}
+
+CONSTCD14
+inline
+weeknum
+year_lastweek_weekday::weeknum() const NOEXCEPT
+{
+    return (y_ / last).weeknum();
+}
+
+CONSTCD11 inline weekday year_lastweek_weekday::weekday() const NOEXCEPT {return wd_;}
+
+CONSTCD14
+inline
+year_lastweek_weekday::operator sys_days() const NOEXCEPT
+{
+    return sys_days(date::year{static_cast<int>(y_)}/date::dec/date::thu[date::last])
+         + (sun - thu) - (sun - wd_);
+}
+
+CONSTCD14
+inline
+year_lastweek_weekday::operator local_days() const NOEXCEPT
+{
+    return local_days(date::year{static_cast<int>(y_)}/date::dec/date::thu[date::last])
+         + (sun - thu) - (sun - wd_);
+}
+
+CONSTCD11
+inline
+bool
+year_lastweek_weekday::ok() const NOEXCEPT
+{
+    return y_.ok() && wd_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.weekday() == y.weekday();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (static_cast<unsigned>(x.weekday()) < static_cast<unsigned>(y.weekday())));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_lastweek_weekday& x, const year_lastweek_weekday& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+year_lastweek_weekday
+operator+(const year_lastweek_weekday& ywnwd, const years& y)  NOEXCEPT
+{
+    return (ywnwd.year() + y) / last / ywnwd.weekday();
+}
+
+CONSTCD11
+inline
+year_lastweek_weekday
+operator+(const years& y, const year_lastweek_weekday& ywnwd)  NOEXCEPT
+{
+    return ywnwd + y;
+}
+
+CONSTCD11
+inline
+year_lastweek_weekday
+operator-(const year_lastweek_weekday& ywnwd, const years& y)  NOEXCEPT
+{
+    return ywnwd + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_lastweek_weekday& ywnwd)
+{
+    return os << ywnwd.year() << "-W last-" << ywnwd.weekday();
+}
+
+// year_weeknum_weekday
+
+CONSTCD11
+inline
+year_weeknum_weekday::year_weeknum_weekday(const iso_week::year& y,
+                                           const iso_week::weeknum& wn,
+                                           const iso_week::weekday& wd) NOEXCEPT
+    : y_(y)
+    , wn_(wn)
+    , wd_(wd)
+    {}
+
+CONSTCD14
+inline
+year_weeknum_weekday::year_weeknum_weekday(const year_lastweek_weekday& ylwwd) NOEXCEPT
+    : y_(ylwwd.year())
+    , wn_(ylwwd.weeknum())
+    , wd_(ylwwd.weekday())
+    {}
+
+CONSTCD14
+inline
+year_weeknum_weekday::year_weeknum_weekday(const sys_days& dp) NOEXCEPT
+    : year_weeknum_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_weeknum_weekday::year_weeknum_weekday(const local_days& dp) NOEXCEPT
+    : year_weeknum_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+inline
+year_weeknum_weekday&
+year_weeknum_weekday::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+inline
+year_weeknum_weekday&
+year_weeknum_weekday::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_weeknum_weekday::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline weeknum year_weeknum_weekday::weeknum() const NOEXCEPT {return wn_;}
+CONSTCD11 inline weekday year_weeknum_weekday::weekday() const NOEXCEPT {return wd_;}
+
+CONSTCD14
+inline
+year_weeknum_weekday::operator sys_days() const NOEXCEPT
+{
+    return sys_days(date::year{static_cast<int>(y_)-1}/date::dec/date::thu[date::last])
+         + (date::mon - date::thu) + weeks{static_cast<unsigned>(wn_)-1} + (wd_ - mon);
+}
+
+CONSTCD14
+inline
+year_weeknum_weekday::operator local_days() const NOEXCEPT
+{
+    return local_days(date::year{static_cast<int>(y_)-1}/date::dec/date::thu[date::last])
+         + (date::mon - date::thu) + weeks{static_cast<unsigned>(wn_)-1} + (wd_ - mon);
+}
+
+CONSTCD14
+inline
+bool
+year_weeknum_weekday::ok() const NOEXCEPT
+{
+    return y_.ok() && wd_.ok() && iso_week::weeknum{1u} <= wn_ && wn_ <= year_lastweek{y_}.weeknum();
+}
+
+CONSTCD14
+inline
+year_weeknum_weekday
+year_weeknum_weekday::from_days(days d) NOEXCEPT
+{
+    const auto dp = sys_days{d};
+    const auto wd = iso_week::weekday{dp};
+    auto y = date::year_month_day{dp + days{3}}.year();
+    auto start = sys_days((y - date::years{1})/date::dec/date::thu[date::last]) + (mon-thu);
+    if (dp < start)
+    {
+        --y;
+        start = sys_days((y - date::years{1})/date::dec/date::thu[date::last]) + (mon-thu);
+    }
+    const auto wn = iso_week::weeknum(
+                       static_cast<unsigned>(date::trunc<weeks>(dp - start).count() + 1));
+    return {iso_week::year(static_cast<int>(y)), wn, wd};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.weeknum() == y.weeknum() && x.weekday() == y.weekday();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.weeknum() < y.weeknum() ? true
+        : (x.weeknum() > y.weeknum() ? false
+        : (static_cast<unsigned>(x.weekday()) < static_cast<unsigned>(y.weekday())))));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_weeknum_weekday& x, const year_weeknum_weekday& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+year_weeknum_weekday
+operator+(const year_weeknum_weekday& ywnwd, const years& y)  NOEXCEPT
+{
+    return (ywnwd.year() + y) / ywnwd.weeknum() / ywnwd.weekday();
+}
+
+CONSTCD11
+inline
+year_weeknum_weekday
+operator+(const years& y, const year_weeknum_weekday& ywnwd)  NOEXCEPT
+{
+    return ywnwd + y;
+}
+
+CONSTCD11
+inline
+year_weeknum_weekday
+operator-(const year_weeknum_weekday& ywnwd, const years& y)  NOEXCEPT
+{
+    return ywnwd + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_weeknum_weekday& ywnwd)
+{
+    return os << ywnwd.year() << '-' << ywnwd.weeknum() << '-' << ywnwd.weekday();
+}
+
+// date composition operators
+
+CONSTCD11
+inline
+year_weeknum
+operator/(const year& y, const weeknum& wn) NOEXCEPT
+{
+    return {y, wn};
+}
+
+CONSTCD11
+inline
+year_weeknum
+operator/(const year& y, int wn) NOEXCEPT
+{
+    return y/weeknum(static_cast<unsigned>(wn));
+}
+
+CONSTCD11
+inline
+year_lastweek
+operator/(const year& y, last_week) NOEXCEPT
+{
+    return year_lastweek{y};
+}
+
+CONSTCD11
+inline
+weeknum_weekday
+operator/(const weeknum& wn, const weekday& wd) NOEXCEPT
+{
+    return {wn, wd};
+}
+
+CONSTCD11
+inline
+weeknum_weekday
+operator/(const weeknum& wn, int wd) NOEXCEPT
+{
+    return wn/weekday{static_cast<unsigned>(wd)};
+}
+
+CONSTCD11
+inline
+weeknum_weekday
+operator/(const weekday& wd, const weeknum& wn) NOEXCEPT
+{
+    return wn/wd;
+}
+
+CONSTCD11
+inline
+weeknum_weekday
+operator/(const weekday& wd, int wn) NOEXCEPT
+{
+    return weeknum{static_cast<unsigned>(wn)}/wd;
+}
+
+CONSTCD11
+inline
+lastweek_weekday
+operator/(const last_week&, const weekday& wd) NOEXCEPT
+{
+    return lastweek_weekday{wd};
+}
+
+CONSTCD11
+inline
+lastweek_weekday
+operator/(const last_week& wn, int wd) NOEXCEPT
+{
+    return wn / weekday{static_cast<unsigned>(wd)};
+}
+
+CONSTCD11
+inline
+lastweek_weekday
+operator/(const weekday& wd, const last_week& wn) NOEXCEPT
+{
+    return wn / wd;
+}
+
+CONSTCD11
+inline
+year_weeknum_weekday
+operator/(const year_weeknum& ywn, const weekday& wd) NOEXCEPT
+{
+    return {ywn.year(), ywn.weeknum(), wd};
+}
+
+CONSTCD11
+inline
+year_weeknum_weekday
+operator/(const year_weeknum& ywn, int wd) NOEXCEPT
+{
+    return ywn / weekday(static_cast<unsigned>(wd));
+}
+
+CONSTCD11
+inline
+year_weeknum_weekday
+operator/(const weeknum_weekday& wnwd, const year& y) NOEXCEPT
+{
+    return {y, wnwd.weeknum(), wnwd.weekday()};
+}
+
+CONSTCD11
+inline
+year_weeknum_weekday
+operator/(const weeknum_weekday& wnwd, int y) NOEXCEPT
+{
+    return wnwd / year{y};
+}
+
+CONSTCD11
+inline
+year_lastweek_weekday
+operator/(const year_lastweek& ylw, const weekday& wd) NOEXCEPT
+{
+    return {ylw.year(), wd};
+}
+
+CONSTCD11
+inline
+year_lastweek_weekday
+operator/(const year_lastweek& ylw, int wd) NOEXCEPT
+{
+    return ylw / weekday(static_cast<unsigned>(wd));
+}
+
+CONSTCD11
+inline
+year_lastweek_weekday
+operator/(const lastweek_weekday& lwwd, const year& y) NOEXCEPT
+{
+    return {y, lwwd.weekday()};
+}
+
+CONSTCD11
+inline
+year_lastweek_weekday
+operator/(const lastweek_weekday& lwwd, int y) NOEXCEPT
+{
+    return lwwd / year{y};
+}
+
+}  // namespace iso_week
+
+#endif  // ISO_WEEK_H
diff --git a/src/libs/date/includes/date/julian.h b/src/libs/date/includes/date/julian.h
new file mode 100644
index 00000000..7869792b
--- /dev/null
+++ b/src/libs/date/includes/date/julian.h
@@ -0,0 +1,3046 @@
+#ifndef JULIAN_H
+#define JULIAN_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2016 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+#include "date.h"
+
+namespace julian
+{
+
+// durations
+
+using days = date::days;
+
+using weeks = date::weeks;
+
+using years = std::chrono::duration
+    <int, date::detail::ratio_multiply<std::ratio<1461, 4>, days::period>>;
+
+using months = std::chrono::duration
+    <int, date::detail::ratio_divide<years::period, std::ratio<12>>>;
+
+// time_point
+
+using sys_days   = date::sys_days;
+using local_days = date::local_days;
+
+// types
+
+struct last_spec
+{
+    explicit last_spec() = default;
+};
+
+class day;
+class month;
+class year;
+
+class weekday;
+class weekday_indexed;
+class weekday_last;
+
+class month_day;
+class month_day_last;
+class month_weekday;
+class month_weekday_last;
+
+class year_month;
+
+class year_month_day;
+class year_month_day_last;
+class year_month_weekday;
+class year_month_weekday_last;
+
+// date composition operators
+
+CONSTCD11 year_month operator/(const year& y, const month& m) NOEXCEPT;
+CONSTCD11 year_month operator/(const year& y, int          m) NOEXCEPT;
+
+CONSTCD11 month_day operator/(const day& d, const month& m) NOEXCEPT;
+CONSTCD11 month_day operator/(const day& d, int          m) NOEXCEPT;
+CONSTCD11 month_day operator/(const month& m, const day& d) NOEXCEPT;
+CONSTCD11 month_day operator/(const month& m, int        d) NOEXCEPT;
+CONSTCD11 month_day operator/(int          m, const day& d) NOEXCEPT;
+
+CONSTCD11 month_day_last operator/(const month& m, last_spec) NOEXCEPT;
+CONSTCD11 month_day_last operator/(int          m, last_spec) NOEXCEPT;
+CONSTCD11 month_day_last operator/(last_spec, const month& m) NOEXCEPT;
+CONSTCD11 month_day_last operator/(last_spec, int          m) NOEXCEPT;
+
+CONSTCD11 month_weekday operator/(const month& m, const weekday_indexed& wdi) NOEXCEPT;
+CONSTCD11 month_weekday operator/(int          m, const weekday_indexed& wdi) NOEXCEPT;
+CONSTCD11 month_weekday operator/(const weekday_indexed& wdi, const month& m) NOEXCEPT;
+CONSTCD11 month_weekday operator/(const weekday_indexed& wdi, int          m) NOEXCEPT;
+
+CONSTCD11 month_weekday_last operator/(const month& m, const weekday_last& wdl) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(int          m, const weekday_last& wdl) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(const weekday_last& wdl, const month& m) NOEXCEPT;
+CONSTCD11 month_weekday_last operator/(const weekday_last& wdl, int          m) NOEXCEPT;
+
+CONSTCD11 year_month_day operator/(const year_month& ym, const day& d) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const year_month& ym, int        d) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const year& y, const month_day& md) NOEXCEPT;
+CONSTCD11 year_month_day operator/(int         y, const month_day& md) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const month_day& md, const year& y) NOEXCEPT;
+CONSTCD11 year_month_day operator/(const month_day& md, int         y) NOEXCEPT;
+
+CONSTCD11
+    year_month_day_last operator/(const year_month& ym,   last_spec) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const year& y, const month_day_last& mdl) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(int         y, const month_day_last& mdl) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const month_day_last& mdl, const year& y) NOEXCEPT;
+CONSTCD11
+    year_month_day_last operator/(const month_day_last& mdl, int         y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const year_month& ym, const weekday_indexed& wdi) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const year&        y, const month_weekday&   mwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(int                y, const month_weekday&   mwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const month_weekday& mwd, const year&          y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator/(const month_weekday& mwd, int                  y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const year_month& ym, const weekday_last& wdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const year& y, const month_weekday_last& mwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(int         y, const month_weekday_last& mwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, const year& y) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, int         y) NOEXCEPT;
+
+// Detailed interface
+
+// day
+
+class day
+{
+    unsigned char d_;
+
+public:
+    explicit CONSTCD11 day(unsigned d) NOEXCEPT;
+
+    CONSTCD14 day& operator++()    NOEXCEPT;
+    CONSTCD14 day  operator++(int) NOEXCEPT;
+    CONSTCD14 day& operator--()    NOEXCEPT;
+    CONSTCD14 day  operator--(int) NOEXCEPT;
+
+    CONSTCD14 day& operator+=(const days& d) NOEXCEPT;
+    CONSTCD14 day& operator-=(const days& d) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const day& x, const day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const day& x, const day& y) NOEXCEPT;
+
+CONSTCD11 day  operator+(const day&  x, const days& y) NOEXCEPT;
+CONSTCD11 day  operator+(const days& x, const day&  y) NOEXCEPT;
+CONSTCD11 day  operator-(const day&  x, const days& y) NOEXCEPT;
+CONSTCD11 days operator-(const day&  x, const day&  y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const day& d);
+
+// month
+
+class month
+{
+    unsigned char m_;
+
+public:
+    explicit CONSTCD11 month(unsigned m) NOEXCEPT;
+
+    CONSTCD14 month& operator++()    NOEXCEPT;
+    CONSTCD14 month  operator++(int) NOEXCEPT;
+    CONSTCD14 month& operator--()    NOEXCEPT;
+    CONSTCD14 month  operator--(int) NOEXCEPT;
+
+    CONSTCD14 month& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 month& operator-=(const months& m) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month& x, const month& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month& x, const month& y) NOEXCEPT;
+
+CONSTCD14 month  operator+(const month&  x, const months& y) NOEXCEPT;
+CONSTCD14 month  operator+(const months& x,  const month& y) NOEXCEPT;
+CONSTCD14 month  operator-(const month&  x, const months& y) NOEXCEPT;
+CONSTCD14 months operator-(const month&  x,  const month& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month& m);
+
+// year
+
+class year
+{
+    short y_;
+
+public:
+    explicit CONSTCD11 year(int y) NOEXCEPT;
+
+    CONSTCD14 year& operator++()    NOEXCEPT;
+    CONSTCD14 year  operator++(int) NOEXCEPT;
+    CONSTCD14 year& operator--()    NOEXCEPT;
+    CONSTCD14 year  operator--(int) NOEXCEPT;
+
+    CONSTCD14 year& operator+=(const years& y) NOEXCEPT;
+    CONSTCD14 year& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 bool is_leap() const NOEXCEPT;
+
+    CONSTCD11 explicit operator int() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+    static CONSTCD11 year min() NOEXCEPT;
+    static CONSTCD11 year max() NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year& x, const year& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year& x, const year& y) NOEXCEPT;
+
+CONSTCD11 year  operator+(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 year  operator+(const years& x, const year&  y) NOEXCEPT;
+CONSTCD11 year  operator-(const year&  x, const years& y) NOEXCEPT;
+CONSTCD11 years operator-(const year&  x, const year&  y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y);
+
+// weekday
+
+class weekday
+{
+    unsigned char wd_;
+public:
+    explicit CONSTCD11 weekday(unsigned wd) NOEXCEPT;
+    explicit weekday(int) = delete;
+    CONSTCD11 weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD11 explicit weekday(const local_days& dp) NOEXCEPT;
+
+    CONSTCD14 weekday& operator++()    NOEXCEPT;
+    CONSTCD14 weekday  operator++(int) NOEXCEPT;
+    CONSTCD14 weekday& operator--()    NOEXCEPT;
+    CONSTCD14 weekday  operator--(int) NOEXCEPT;
+
+    CONSTCD14 weekday& operator+=(const days& d) NOEXCEPT;
+    CONSTCD14 weekday& operator-=(const days& d) NOEXCEPT;
+
+    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+    CONSTCD11 weekday_indexed operator[](unsigned index) const NOEXCEPT;
+    CONSTCD11 weekday_last    operator[](last_spec)      const NOEXCEPT;
+
+private:
+    static CONSTCD11 unsigned char weekday_from_days(int z) NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday& x, const weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday& x, const weekday& y) NOEXCEPT;
+
+CONSTCD14 weekday operator+(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 weekday operator+(const days&    x, const weekday& y) NOEXCEPT;
+CONSTCD14 weekday operator-(const weekday& x, const days&    y) NOEXCEPT;
+CONSTCD14 days    operator-(const weekday& x, const weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd);
+
+// weekday_indexed
+
+class weekday_indexed
+{
+    unsigned char wd_    : 4;
+    unsigned char index_ : 4;
+
+public:
+    CONSTCD11 weekday_indexed(const julian::weekday& wd, unsigned index) NOEXCEPT;
+
+    CONSTCD11 julian::weekday weekday() const NOEXCEPT;
+    CONSTCD11 unsigned index() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_indexed& wdi);
+
+// weekday_last
+
+class weekday_last
+{
+    julian::weekday wd_;
+
+public:
+    explicit CONSTCD11 weekday_last(const julian::weekday& wd) NOEXCEPT;
+
+    CONSTCD11 julian::weekday weekday() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const weekday_last& x, const weekday_last& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const weekday_last& x, const weekday_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_last& wdl);
+
+// year_month
+
+class year_month
+{
+    julian::year  y_;
+    julian::month m_;
+
+public:
+    CONSTCD11 year_month(const julian::year& y, const julian::month& m) NOEXCEPT;
+
+    CONSTCD11 julian::year  year()  const NOEXCEPT;
+    CONSTCD11 julian::month month() const NOEXCEPT;
+
+    CONSTCD14 year_month& operator+=(const months& dm) NOEXCEPT;
+    CONSTCD14 year_month& operator-=(const months& dm) NOEXCEPT;
+    CONSTCD14 year_month& operator+=(const years& dy) NOEXCEPT;
+    CONSTCD14 year_month& operator-=(const years& dy) NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_month& x, const year_month& y) NOEXCEPT;
+
+CONSTCD14 year_month operator+(const year_month& ym, const months& dm) NOEXCEPT;
+CONSTCD14 year_month operator+(const months& dm, const year_month& ym) NOEXCEPT;
+CONSTCD14 year_month operator-(const year_month& ym, const months& dm) NOEXCEPT;
+
+CONSTCD11 months operator-(const year_month& x, const year_month& y) NOEXCEPT;
+CONSTCD11 year_month operator+(const year_month& ym, const years& dy) NOEXCEPT;
+CONSTCD11 year_month operator+(const years& dy, const year_month& ym) NOEXCEPT;
+CONSTCD11 year_month operator-(const year_month& ym, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month& ym);
+
+// month_day
+
+class month_day
+{
+    julian::month m_;
+    julian::day   d_;
+
+public:
+    CONSTCD11 month_day(const julian::month& m, const julian::day& d) NOEXCEPT;
+
+    CONSTCD11 julian::month month() const NOEXCEPT;
+    CONSTCD11 julian::day   day() const NOEXCEPT;
+
+    CONSTCD14 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month_day& x, const month_day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month_day& x, const month_day& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day& md);
+
+// month_day_last
+
+class month_day_last
+{
+    julian::month m_;
+
+public:
+    CONSTCD11 explicit month_day_last(const julian::month& m) NOEXCEPT;
+
+    CONSTCD11 julian::month month() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator< (const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator> (const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const month_day_last& x, const month_day_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day_last& mdl);
+
+// month_weekday
+
+class month_weekday
+{
+    julian::month           m_;
+    julian::weekday_indexed wdi_;
+public:
+    CONSTCD11 month_weekday(const julian::month& m,
+                            const julian::weekday_indexed& wdi) NOEXCEPT;
+
+    CONSTCD11 julian::month           month()           const NOEXCEPT;
+    CONSTCD11 julian::weekday_indexed weekday_indexed() const NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const month_weekday& x, const month_weekday& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const month_weekday& x, const month_weekday& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday& mwd);
+
+// month_weekday_last
+
+class month_weekday_last
+{
+    julian::month        m_;
+    julian::weekday_last wdl_;
+
+public:
+    CONSTCD11 month_weekday_last(const julian::month& m,
+                                 const julian::weekday_last& wd) NOEXCEPT;
+
+    CONSTCD11 julian::month        month()        const NOEXCEPT;
+    CONSTCD11 julian::weekday_last weekday_last() const NOEXCEPT;
+
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday_last& mwdl);
+
+// class year_month_day
+
+class year_month_day
+{
+    julian::year  y_;
+    julian::month m_;
+    julian::day   d_;
+
+public:
+    CONSTCD11 year_month_day(const julian::year& y, const julian::month& m,
+                             const julian::day& d) NOEXCEPT;
+    CONSTCD14 year_month_day(const year_month_day_last& ymdl) NOEXCEPT;
+
+    CONSTCD14 year_month_day(sys_days dp) NOEXCEPT;
+    CONSTCD14 explicit year_month_day(local_days dp) NOEXCEPT;
+
+    CONSTCD14 year_month_day& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_day& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 julian::year  year()  const NOEXCEPT;
+    CONSTCD11 julian::month month() const NOEXCEPT;
+    CONSTCD11 julian::day   day()   const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD14 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD14 year_month_day from_days(days dp) NOEXCEPT;
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11 bool operator==(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator!=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator< (const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator> (const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator<=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+CONSTCD11 bool operator>=(const year_month_day& x, const year_month_day& y) NOEXCEPT;
+
+CONSTCD14 year_month_day operator+(const year_month_day& ymd, const months& dm) NOEXCEPT;
+CONSTCD14 year_month_day operator+(const months& dm, const year_month_day& ymd) NOEXCEPT;
+CONSTCD14 year_month_day operator-(const year_month_day& ymd, const months& dm) NOEXCEPT;
+CONSTCD11 year_month_day operator+(const year_month_day& ymd, const years& dy)  NOEXCEPT;
+CONSTCD11 year_month_day operator+(const years& dy, const year_month_day& ymd)  NOEXCEPT;
+CONSTCD11 year_month_day operator-(const year_month_day& ymd, const years& dy)  NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day& ymd);
+
+// year_month_day_last
+
+class year_month_day_last
+{
+    julian::year           y_;
+    julian::month_day_last mdl_;
+
+public:
+    CONSTCD11 year_month_day_last(const julian::year& y,
+                                  const julian::month_day_last& mdl) NOEXCEPT;
+
+    CONSTCD14 year_month_day_last& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_day_last& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 julian::year           year()           const NOEXCEPT;
+    CONSTCD11 julian::month          month()          const NOEXCEPT;
+    CONSTCD11 julian::month_day_last month_day_last() const NOEXCEPT;
+    CONSTCD14 julian::day            day()            const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator< (const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator> (const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator<=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+CONSTCD11
+    bool operator>=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT;
+
+CONSTCD14
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const months& dm) NOEXCEPT;
+
+CONSTCD14
+year_month_day_last
+operator+(const months& dm, const year_month_day_last& ymdl) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator+(const years& dy, const year_month_day_last& ymdl) NOEXCEPT;
+
+CONSTCD14
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day_last& ymdl);
+
+// year_month_weekday
+
+class year_month_weekday
+{
+    julian::year            y_;
+    julian::month           m_;
+    julian::weekday_indexed wdi_;
+
+public:
+    CONSTCD11 year_month_weekday(const julian::year& y, const julian::month& m,
+                                   const julian::weekday_indexed& wdi) NOEXCEPT;
+    CONSTCD14 year_month_weekday(const sys_days& dp) NOEXCEPT;
+    CONSTCD14 explicit year_month_weekday(const local_days& dp) NOEXCEPT;
+
+    CONSTCD14 year_month_weekday& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator+=(const years& y)  NOEXCEPT;
+    CONSTCD14 year_month_weekday& operator-=(const years& y)  NOEXCEPT;
+
+    CONSTCD11 julian::year year() const NOEXCEPT;
+    CONSTCD11 julian::month month() const NOEXCEPT;
+    CONSTCD11 julian::weekday weekday() const NOEXCEPT;
+    CONSTCD11 unsigned index() const NOEXCEPT;
+    CONSTCD11 julian::weekday_indexed weekday_indexed() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD14 bool ok() const NOEXCEPT;
+
+private:
+    static CONSTCD14 year_month_weekday from_days(days dp) NOEXCEPT;
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11
+    bool operator==(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT;
+CONSTCD11
+    bool operator!=(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const months& dm) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday
+operator+(const months& dm, const year_month_weekday& ymwd) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator+(const years& dy, const year_month_weekday& ymwd) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday& ymwdi);
+
+// year_month_weekday_last
+
+class year_month_weekday_last
+{
+    julian::year y_;
+    julian::month m_;
+    julian::weekday_last wdl_;
+
+public:
+    CONSTCD11 year_month_weekday_last(const julian::year& y, const julian::month& m,
+                                      const julian::weekday_last& wdl) NOEXCEPT;
+
+    CONSTCD14 year_month_weekday_last& operator+=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator-=(const months& m) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator+=(const years& y) NOEXCEPT;
+    CONSTCD14 year_month_weekday_last& operator-=(const years& y) NOEXCEPT;
+
+    CONSTCD11 julian::year year() const NOEXCEPT;
+    CONSTCD11 julian::month month() const NOEXCEPT;
+    CONSTCD11 julian::weekday weekday() const NOEXCEPT;
+    CONSTCD11 julian::weekday_last weekday_last() const NOEXCEPT;
+
+    CONSTCD14 operator sys_days() const NOEXCEPT;
+    CONSTCD14 explicit operator local_days() const NOEXCEPT;
+    CONSTCD11 bool ok() const NOEXCEPT;
+
+private:
+    CONSTCD14 days to_days() const NOEXCEPT;
+};
+
+CONSTCD11
+bool
+operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT;
+
+CONSTCD11
+bool
+operator!=(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday_last
+operator+(const months& dm, const year_month_weekday_last& ymwdl) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator+(const years& dy, const year_month_weekday_last& ymwdl) NOEXCEPT;
+
+CONSTCD14
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT;
+
+CONSTCD11
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT;
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday_last& ymwdl);
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+inline namespace literals
+{
+
+CONSTCD11 julian::day  operator "" _d(unsigned long long d) NOEXCEPT;
+CONSTCD11 julian::year operator "" _y(unsigned long long y) NOEXCEPT;
+
+// CONSTDATA julian::month jan{1};
+// CONSTDATA julian::month feb{2};
+// CONSTDATA julian::month mar{3};
+// CONSTDATA julian::month apr{4};
+// CONSTDATA julian::month may{5};
+// CONSTDATA julian::month jun{6};
+// CONSTDATA julian::month jul{7};
+// CONSTDATA julian::month aug{8};
+// CONSTDATA julian::month sep{9};
+// CONSTDATA julian::month oct{10};
+// CONSTDATA julian::month nov{11};
+// CONSTDATA julian::month dec{12};
+
+}  // inline namespace literals
+#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+//----------------+
+// Implementation |
+//----------------+
+
+// day
+
+CONSTCD11 inline day::day(unsigned d) NOEXCEPT : d_(static_cast<unsigned char>(d)) {}
+CONSTCD14 inline day& day::operator++() NOEXCEPT {++d_; return *this;}
+CONSTCD14 inline day day::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline day& day::operator--() NOEXCEPT {--d_; return *this;}
+CONSTCD14 inline day day::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+CONSTCD14 inline day& day::operator+=(const days& d) NOEXCEPT {*this = *this + d; return *this;}
+CONSTCD14 inline day& day::operator-=(const days& d) NOEXCEPT {*this = *this - d; return *this;}
+CONSTCD11 inline day::operator unsigned() const NOEXCEPT {return d_;}
+CONSTCD11 inline bool day::ok() const NOEXCEPT {return 1 <= d_ && d_ <= 31;}
+
+CONSTCD11
+inline
+bool
+operator==(const day& x, const day& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const day& x, const day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const day& x, const day& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const day& x, const day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const day& x, const day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const day& x, const day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+days
+operator-(const day& x, const day& y) NOEXCEPT
+{
+    return days{static_cast<days::rep>(static_cast<unsigned>(x)
+                                     - static_cast<unsigned>(y))};
+}
+
+CONSTCD11
+inline
+day
+operator+(const day& x, const days& y) NOEXCEPT
+{
+    return day{static_cast<unsigned>(x) + static_cast<unsigned>(y.count())};
+}
+
+CONSTCD11
+inline
+day
+operator+(const days& x, const day& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+day
+operator-(const day& x, const days& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const day& d)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::right);
+    os.width(2);
+    os << static_cast<unsigned>(d);
+    return os;
+}
+
+// month
+
+CONSTCD11 inline month::month(unsigned m) NOEXCEPT : m_(static_cast<decltype(m_)>(m)) {}
+CONSTCD14 inline month& month::operator++() NOEXCEPT {if (++m_ == 13) m_ = 1; return *this;}
+CONSTCD14 inline month month::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline month& month::operator--() NOEXCEPT {if (--m_ == 0) m_ = 12; return *this;}
+CONSTCD14 inline month month::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+CONSTCD14
+inline
+month&
+month::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+month&
+month::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD11 inline month::operator unsigned() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool month::ok() const NOEXCEPT {return 1 <= m_ && m_ <= 12;}
+
+CONSTCD11
+inline
+bool
+operator==(const month& x, const month& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month& x, const month& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month& x, const month& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month& x, const month& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month& x, const month& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month& x, const month& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD14
+inline
+months
+operator-(const month& x, const month& y) NOEXCEPT
+{
+    auto const d = static_cast<unsigned>(x) - static_cast<unsigned>(y);
+    return months(d <= 11 ? d : d + 12);
+}
+
+CONSTCD14
+inline
+month
+operator+(const month& x, const months& y) NOEXCEPT
+{
+    auto const mu = static_cast<long long>(static_cast<unsigned>(x)) - 1 + y.count();
+    auto const yr = (mu >= 0 ? mu : mu-11) / 12;
+    return month{static_cast<unsigned>(mu - yr * 12 + 1)};
+}
+
+CONSTCD14
+inline
+month
+operator+(const months& x, const month& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD14
+inline
+month
+operator-(const month& x, const months& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month& m)
+{
+    switch (static_cast<unsigned>(m))
+    {
+    case 1:
+        os << "Jan";
+        break;
+    case 2:
+        os << "Feb";
+        break;
+    case 3:
+        os << "Mar";
+        break;
+    case 4:
+        os << "Apr";
+        break;
+    case 5:
+        os << "May";
+        break;
+    case 6:
+        os << "Jun";
+        break;
+    case 7:
+        os << "Jul";
+        break;
+    case 8:
+        os << "Aug";
+        break;
+    case 9:
+        os << "Sep";
+        break;
+    case 10:
+        os << "Oct";
+        break;
+    case 11:
+        os << "Nov";
+        break;
+    case 12:
+        os << "Dec";
+        break;
+    default:
+        os << static_cast<unsigned>(m) << " is not a valid month";
+        break;
+    }
+    return os;
+}
+
+// year
+
+CONSTCD11 inline year::year(int y) NOEXCEPT : y_(static_cast<decltype(y_)>(y)) {}
+CONSTCD14 inline year& year::operator++() NOEXCEPT {++y_; return *this;}
+CONSTCD14 inline year year::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline year& year::operator--() NOEXCEPT {--y_; return *this;}
+CONSTCD14 inline year year::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+CONSTCD14 inline year& year::operator+=(const years& y) NOEXCEPT {*this = *this + y; return *this;}
+CONSTCD14 inline year& year::operator-=(const years& y) NOEXCEPT {*this = *this - y; return *this;}
+
+CONSTCD11
+inline
+bool
+year::is_leap() const NOEXCEPT
+{
+    return y_ % 4 == 0;
+}
+
+CONSTCD11 inline year::operator int() const NOEXCEPT {return y_;}
+CONSTCD11 inline bool year::ok() const NOEXCEPT {return true;}
+
+CONSTCD11
+inline
+year
+year::min() NOEXCEPT
+{
+    return year{std::numeric_limits<short>::min()};
+}
+
+CONSTCD11
+inline
+year
+year::max() NOEXCEPT
+{
+    return year{std::numeric_limits<short>::max()};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) == static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year& x, const year& y) NOEXCEPT
+{
+    return static_cast<int>(x) < static_cast<int>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year& x, const year& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year& x, const year& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year& x, const year& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD11
+inline
+years
+operator-(const year& x, const year& y) NOEXCEPT
+{
+    return years{static_cast<int>(x) - static_cast<int>(y)};
+}
+
+CONSTCD11
+inline
+year
+operator+(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) + y.count()};
+}
+
+CONSTCD11
+inline
+year
+operator+(const years& x, const year& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD11
+inline
+year
+operator-(const year& x, const years& y) NOEXCEPT
+{
+    return year{static_cast<int>(x) - y.count()};
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year& y)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::internal);
+    os.width(4 + (y < year{0}));
+    os << static_cast<int>(y);
+    return os;
+}
+
+// weekday
+
+CONSTCD11
+inline
+unsigned char
+weekday::weekday_from_days(int z) NOEXCEPT
+{
+    return static_cast<unsigned char>(static_cast<unsigned>(
+        z >= -4 ? (z+4) % 7 : (z+5) % 7 + 6));
+}
+
+CONSTCD11
+inline
+weekday::weekday(unsigned wd) NOEXCEPT
+    : wd_(static_cast<decltype(wd_)>(wd))
+    {}
+
+CONSTCD11
+inline
+weekday::weekday(const sys_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+CONSTCD11
+inline
+weekday::weekday(const local_days& dp) NOEXCEPT
+    : wd_(weekday_from_days(dp.time_since_epoch().count()))
+    {}
+
+CONSTCD14 inline weekday& weekday::operator++() NOEXCEPT {if (++wd_ == 7) wd_ = 0; return *this;}
+CONSTCD14 inline weekday weekday::operator++(int) NOEXCEPT {auto tmp(*this); ++(*this); return tmp;}
+CONSTCD14 inline weekday& weekday::operator--() NOEXCEPT {if (wd_-- == 0) wd_ = 6; return *this;}
+CONSTCD14 inline weekday weekday::operator--(int) NOEXCEPT {auto tmp(*this); --(*this); return tmp;}
+
+CONSTCD14
+inline
+weekday&
+weekday::operator+=(const days& d) NOEXCEPT
+{
+    *this = *this + d;
+    return *this;
+}
+
+CONSTCD14
+inline
+weekday&
+weekday::operator-=(const days& d) NOEXCEPT
+{
+    *this = *this - d;
+    return *this;
+}
+
+CONSTCD11
+inline
+weekday::operator unsigned() const NOEXCEPT
+{
+    return static_cast<unsigned>(wd_);
+}
+
+CONSTCD11 inline bool weekday::ok() const NOEXCEPT {return wd_ <= 6;}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday& x, const weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD14
+inline
+days
+operator-(const weekday& x, const weekday& y) NOEXCEPT
+{
+    auto const diff = static_cast<unsigned>(x) - static_cast<unsigned>(y);
+    return days{diff <= 6 ? diff : diff + 7};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const weekday& x, const days& y) NOEXCEPT
+{
+    auto const wdu = static_cast<long long>(static_cast<unsigned>(x)) + y.count();
+    auto const wk = (wdu >= 0 ? wdu : wdu-6) / 7;
+    return weekday{static_cast<unsigned>(wdu - wk * 7)};
+}
+
+CONSTCD14
+inline
+weekday
+operator+(const days& x, const weekday& y) NOEXCEPT
+{
+    return y + x;
+}
+
+CONSTCD14
+inline
+weekday
+operator-(const weekday& x, const days& y) NOEXCEPT
+{
+    return x + -y;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday& wd)
+{
+    switch (static_cast<unsigned>(wd))
+    {
+    case 0:
+        os << "Sun";
+        break;
+    case 1:
+        os << "Mon";
+        break;
+    case 2:
+        os << "Tue";
+        break;
+    case 3:
+        os << "Wed";
+        break;
+    case 4:
+        os << "Thu";
+        break;
+    case 5:
+        os << "Fri";
+        break;
+    case 6:
+        os << "Sat";
+        break;
+    default:
+        os << static_cast<unsigned>(wd) << " is not a valid weekday";
+        break;
+    }
+    return os;
+}
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+inline namespace literals
+{
+
+CONSTCD11
+inline
+julian::day
+operator "" _d(unsigned long long d) NOEXCEPT
+{
+    return julian::day{static_cast<unsigned>(d)};
+}
+
+CONSTCD11
+inline
+julian::year
+operator "" _y(unsigned long long y) NOEXCEPT
+{
+    return julian::year(static_cast<int>(y));
+}
+#endif  // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+CONSTDATA julian::last_spec last{};
+
+CONSTDATA julian::month jan{1};
+CONSTDATA julian::month feb{2};
+CONSTDATA julian::month mar{3};
+CONSTDATA julian::month apr{4};
+CONSTDATA julian::month may{5};
+CONSTDATA julian::month jun{6};
+CONSTDATA julian::month jul{7};
+CONSTDATA julian::month aug{8};
+CONSTDATA julian::month sep{9};
+CONSTDATA julian::month oct{10};
+CONSTDATA julian::month nov{11};
+CONSTDATA julian::month dec{12};
+
+CONSTDATA julian::weekday sun{0u};
+CONSTDATA julian::weekday mon{1u};
+CONSTDATA julian::weekday tue{2u};
+CONSTDATA julian::weekday wed{3u};
+CONSTDATA julian::weekday thu{4u};
+CONSTDATA julian::weekday fri{5u};
+CONSTDATA julian::weekday sat{6u};
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+}  // inline namespace literals
+#endif
+
+// weekday_indexed
+
+CONSTCD11
+inline
+weekday
+weekday_indexed::weekday() const NOEXCEPT
+{
+    return julian::weekday{static_cast<unsigned>(wd_)};
+}
+
+CONSTCD11 inline unsigned weekday_indexed::index() const NOEXCEPT {return index_;}
+
+CONSTCD11
+inline
+bool
+weekday_indexed::ok() const NOEXCEPT
+{
+    return weekday().ok() && 1 <= index_ && index_ <= 5;
+}
+
+CONSTCD11
+inline
+weekday_indexed::weekday_indexed(const julian::weekday& wd, unsigned index) NOEXCEPT
+    : wd_(static_cast<decltype(wd_)>(static_cast<unsigned>(wd)))
+    , index_(static_cast<decltype(index_)>(index))
+    {}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_indexed& wdi)
+{
+    return os << wdi.weekday() << '[' << wdi.index() << ']';
+}
+
+CONSTCD11
+inline
+weekday_indexed
+weekday::operator[](unsigned index) const NOEXCEPT
+{
+    return {*this, index};
+}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT
+{
+    return x.weekday() == y.weekday() && x.index() == y.index();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday_indexed& x, const weekday_indexed& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+// weekday_last
+
+CONSTCD11 inline julian::weekday weekday_last::weekday() const NOEXCEPT {return wd_;}
+CONSTCD11 inline bool weekday_last::ok() const NOEXCEPT {return wd_.ok();}
+CONSTCD11 inline weekday_last::weekday_last(const julian::weekday& wd) NOEXCEPT : wd_(wd) {}
+
+CONSTCD11
+inline
+bool
+operator==(const weekday_last& x, const weekday_last& y) NOEXCEPT
+{
+    return x.weekday() == y.weekday();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const weekday_last& x, const weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const weekday_last& wdl)
+{
+    return os << wdl.weekday() << "[last]";
+}
+
+CONSTCD11
+inline
+weekday_last
+weekday::operator[](last_spec) const NOEXCEPT
+{
+    return weekday_last{*this};
+}
+
+// year_month
+
+CONSTCD11
+inline
+year_month::year_month(const julian::year& y, const julian::month& m) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    {}
+
+CONSTCD11 inline year year_month::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool year_month::ok() const NOEXCEPT {return y_.ok() && m_.ok();}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator+=(const months& dm) NOEXCEPT
+{
+    *this = *this + dm;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator-=(const months& dm) NOEXCEPT
+{
+    *this = *this - dm;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator+=(const years& dy) NOEXCEPT
+{
+    *this = *this + dy;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month&
+year_month::operator-=(const years& dy) NOEXCEPT
+{
+    *this = *this - dy;
+    return *this;
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month() < y.month()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+CONSTCD14
+inline
+year_month
+operator+(const year_month& ym, const months& dm) NOEXCEPT
+{
+    auto dmi = static_cast<int>(static_cast<unsigned>(ym.month())) - 1 + dm.count();
+    auto dy = (dmi >= 0 ? dmi : dmi-11) / 12;
+    dmi = dmi - dy * 12 + 1;
+    return (ym.year() + years(dy)) / month(static_cast<unsigned>(dmi));
+}
+
+CONSTCD14
+inline
+year_month
+operator+(const months& dm, const year_month& ym) NOEXCEPT
+{
+    return ym + dm;
+}
+
+CONSTCD14
+inline
+year_month
+operator-(const year_month& ym, const months& dm) NOEXCEPT
+{
+    return ym + -dm;
+}
+
+CONSTCD11
+inline
+months
+operator-(const year_month& x, const year_month& y) NOEXCEPT
+{
+    return (x.year() - y.year()) +
+            months(static_cast<unsigned>(x.month()) - static_cast<unsigned>(y.month()));
+}
+
+CONSTCD11
+inline
+year_month
+operator+(const year_month& ym, const years& dy) NOEXCEPT
+{
+    return (ym.year() + dy) / ym.month();
+}
+
+CONSTCD11
+inline
+year_month
+operator+(const years& dy, const year_month& ym) NOEXCEPT
+{
+    return ym + dy;
+}
+
+CONSTCD11
+inline
+year_month
+operator-(const year_month& ym, const years& dy) NOEXCEPT
+{
+    return ym + -dy;
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month& ym)
+{
+    return os << ym.year() << '/' << ym.month();
+}
+
+// month_day
+
+CONSTCD11
+inline
+month_day::month_day(const julian::month& m, const julian::day& d) NOEXCEPT
+    : m_(m)
+    , d_(d)
+    {}
+
+CONSTCD11 inline julian::month month_day::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline julian::day month_day::day() const NOEXCEPT {return d_;}
+
+CONSTCD14
+inline
+bool
+month_day::ok() const NOEXCEPT
+{
+    CONSTDATA julian::day d[] =
+        {31_d, 29_d, 31_d, 30_d, 31_d, 30_d, 31_d, 31_d, 30_d, 31_d, 30_d, 31_d};
+    return m_.ok() && 1_d <= d_ && d_ <= d[static_cast<unsigned>(m_)-1];
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.day() == y.day();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return x.month() < y.month() ? true
+        : (x.month() > y.month() ? false
+        : (x.day() < y.day()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month_day& x, const month_day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day& md)
+{
+    return os << md.month() << '/' << md.day();
+}
+
+// month_day_last
+
+CONSTCD11 inline month month_day_last::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline bool month_day_last::ok() const NOEXCEPT {return m_.ok();}
+CONSTCD11 inline month_day_last::month_day_last(const julian::month& m) NOEXCEPT : m_(m) {}
+
+CONSTCD11
+inline
+bool
+operator==(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return x.month() == y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return x.month() < y.month();
+}
+
+CONSTCD11
+inline
+bool
+operator>(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const month_day_last& x, const month_day_last& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_day_last& mdl)
+{
+    return os << mdl.month() << "/last";
+}
+
+// month_weekday
+
+CONSTCD11
+inline
+month_weekday::month_weekday(const julian::month& m,
+                             const julian::weekday_indexed& wdi) NOEXCEPT
+    : m_(m)
+    , wdi_(wdi)
+    {}
+
+CONSTCD11 inline month month_weekday::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday_indexed
+month_weekday::weekday_indexed() const NOEXCEPT
+{
+    return wdi_;
+}
+
+CONSTCD11
+inline
+bool
+month_weekday::ok() const NOEXCEPT
+{
+    return m_.ok() && wdi_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_weekday& x, const month_weekday& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.weekday_indexed() == y.weekday_indexed();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_weekday& x, const month_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday& mwd)
+{
+    return os << mwd.month() << '/' << mwd.weekday_indexed();
+}
+
+// month_weekday_last
+
+CONSTCD11
+inline
+month_weekday_last::month_weekday_last(const julian::month& m,
+                                       const julian::weekday_last& wdl) NOEXCEPT
+    : m_(m)
+    , wdl_(wdl)
+    {}
+
+CONSTCD11 inline month month_weekday_last::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday_last
+month_weekday_last::weekday_last() const NOEXCEPT
+{
+    return wdl_;
+}
+
+CONSTCD11
+inline
+bool
+month_weekday_last::ok() const NOEXCEPT
+{
+    return m_.ok() && wdl_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT
+{
+    return x.month() == y.month() && x.weekday_last() == y.weekday_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const month_weekday_last& x, const month_weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const month_weekday_last& mwdl)
+{
+    return os << mwdl.month() << '/' << mwdl.weekday_last();
+}
+
+// year_month_day_last
+
+CONSTCD11
+inline
+year_month_day_last::year_month_day_last(const julian::year& y,
+                                         const julian::month_day_last& mdl) NOEXCEPT
+    : y_(y)
+    , mdl_(mdl)
+    {}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day_last&
+year_month_day_last::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_day_last::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_day_last::month() const NOEXCEPT {return mdl_.month();}
+
+CONSTCD11
+inline
+month_day_last
+year_month_day_last::month_day_last() const NOEXCEPT
+{
+    return mdl_;
+}
+
+CONSTCD14
+inline
+day
+year_month_day_last::day() const NOEXCEPT
+{
+    CONSTDATA julian::day d[] =
+        {31_d, 28_d, 31_d, 30_d, 31_d, 30_d, 31_d, 31_d, 30_d, 31_d, 30_d, 31_d};
+    return month() != feb || !y_.is_leap() ? d[static_cast<unsigned>(month())-1] : 29_d;
+}
+
+CONSTCD14
+inline
+year_month_day_last::operator sys_days() const NOEXCEPT
+{
+    return sys_days(year()/month()/day());
+}
+
+CONSTCD14
+inline
+year_month_day_last::operator local_days() const NOEXCEPT
+{
+    return local_days(year()/month()/day());
+}
+
+CONSTCD11
+inline
+bool
+year_month_day_last::ok() const NOEXCEPT
+{
+    return y_.ok() && mdl_.ok();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month_day_last() == y.month_day_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month_day_last() < y.month_day_last()));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month_day_last& x, const year_month_day_last& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day_last& ymdl)
+{
+    return os << ymdl.year() << '/' << ymdl.month_day_last();
+}
+
+CONSTCD14
+inline
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const months& dm) NOEXCEPT
+{
+    return (ymdl.year() / ymdl.month() + dm) / last;
+}
+
+CONSTCD14
+inline
+year_month_day_last
+operator+(const months& dm, const year_month_day_last& ymdl) NOEXCEPT
+{
+    return ymdl + dm;
+}
+
+CONSTCD14
+inline
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const months& dm) NOEXCEPT
+{
+    return ymdl + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator+(const year_month_day_last& ymdl, const years& dy) NOEXCEPT
+{
+    return {ymdl.year()+dy, ymdl.month_day_last()};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator+(const years& dy, const year_month_day_last& ymdl) NOEXCEPT
+{
+    return ymdl + dy;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator-(const year_month_day_last& ymdl, const years& dy) NOEXCEPT
+{
+    return ymdl + (-dy);
+}
+
+// year_month_day
+
+CONSTCD11
+inline
+year_month_day::year_month_day(const julian::year& y, const julian::month& m,
+                               const julian::day& d) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , d_(d)
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(const year_month_day_last& ymdl) NOEXCEPT
+    : y_(ymdl.year())
+    , m_(ymdl.month())
+    , d_(ymdl.day())
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(sys_days dp) NOEXCEPT
+    : year_month_day(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_day::year_month_day(local_days dp) NOEXCEPT
+    : year_month_day(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD11 inline year year_month_day::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_day::month() const NOEXCEPT {return m_;}
+CONSTCD11 inline day year_month_day::day() const NOEXCEPT {return d_;}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_day&
+year_month_day::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD14
+inline
+days
+year_month_day::to_days() const NOEXCEPT
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18,
+             "This algorithm has not been ported to a 16 bit unsigned integer");
+    static_assert(std::numeric_limits<int>::digits >= 20,
+             "This algorithm has not been ported to a 16 bit signed integer");
+    auto const y = static_cast<int>(y_) - (m_ <= feb);
+    auto const m = static_cast<unsigned>(m_);
+    auto const d = static_cast<unsigned>(d_);
+    auto const era = (y >= 0 ? y : y-3) / 4;
+    auto const yoe = static_cast<unsigned>(y - era * 4);       // [0, 3]
+    auto const doy = (153*(m > 2 ? m-3 : m+9) + 2)/5 + d-1;    // [0, 365]
+    auto const doe = yoe * 365 + doy;                          // [0, 1460]
+    return days{era * 1461 + static_cast<int>(doe) - 719470};
+}
+
+CONSTCD14
+inline
+year_month_day::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_day::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD14
+inline
+bool
+year_month_day::ok() const NOEXCEPT
+{
+    if (!(y_.ok() && m_.ok()))
+        return false;
+    return 1_d <= d_ && d_ <= (y_/m_/last).day();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() && x.day() == y.day();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+CONSTCD11
+inline
+bool
+operator<(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return x.year() < y.year() ? true
+        : (x.year() > y.year() ? false
+        : (x.month() < y.month() ? true
+        : (x.month() > y.month() ? false
+        : (x.day() < y.day()))));
+}
+
+CONSTCD11
+inline
+bool
+operator>(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return y < x;
+}
+
+CONSTCD11
+inline
+bool
+operator<=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(y < x);
+}
+
+CONSTCD11
+inline
+bool
+operator>=(const year_month_day& x, const year_month_day& y) NOEXCEPT
+{
+    return !(x < y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_day& ymd)
+{
+    date::detail::save_ostream<CharT, Traits> _(os);
+    os.fill('0');
+    os.flags(std::ios::dec | std::ios::right);
+    os << ymd.year() << '-';
+    os.width(2);
+    os << static_cast<unsigned>(ymd.month()) << '-';
+    os << ymd.day();
+    return os;
+}
+
+CONSTCD14
+inline
+year_month_day
+year_month_day::from_days(days dp) NOEXCEPT
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18,
+             "This algorithm has not been ported to a 16 bit unsigned integer");
+    static_assert(std::numeric_limits<int>::digits >= 20,
+             "This algorithm has not been ported to a 16 bit signed integer");
+    auto const z = dp.count() + 719470;
+    auto const era = (z >= 0 ? z : z - 1460) / 1461;
+    auto const doe = static_cast<unsigned>(z - era * 1461);          // [0, 1460]
+    auto const yoe = (doe - doe/1460) / 365;                         // [0, 3]
+    auto const y = static_cast<sys_days::rep>(yoe) + era * 4;
+    auto const doy = doe - 365*yoe;                                  // [0, 365]
+    auto const mp = (5*doy + 2)/153;                                 // [0, 11]
+    auto const d = doy - (153*mp+2)/5 + 1;                           // [1, 31]
+    auto const m = mp < 10 ? mp+3 : mp-9;                            // [1, 12]
+    return year_month_day{julian::year{y + (m <= 2)}, julian::month(m), julian::day(d)};
+}
+
+CONSTCD14
+inline
+year_month_day
+operator+(const year_month_day& ymd, const months& dm) NOEXCEPT
+{
+    return (ymd.year() / ymd.month() + dm) / ymd.day();
+}
+
+CONSTCD14
+inline
+year_month_day
+operator+(const months& dm, const year_month_day& ymd) NOEXCEPT
+{
+    return ymd + dm;
+}
+
+CONSTCD14
+inline
+year_month_day
+operator-(const year_month_day& ymd, const months& dm) NOEXCEPT
+{
+    return ymd + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_day
+operator+(const year_month_day& ymd, const years& dy) NOEXCEPT
+{
+    return (ymd.year() + dy) / ymd.month() / ymd.day();
+}
+
+CONSTCD11
+inline
+year_month_day
+operator+(const years& dy, const year_month_day& ymd) NOEXCEPT
+{
+    return ymd + dy;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator-(const year_month_day& ymd, const years& dy) NOEXCEPT
+{
+    return ymd + (-dy);
+}
+
+// year_month_weekday
+
+CONSTCD11
+inline
+year_month_weekday::year_month_weekday(const julian::year& y, const julian::month& m,
+                                       const julian::weekday_indexed& wdi)
+        NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , wdi_(wdi)
+    {}
+
+CONSTCD14
+inline
+year_month_weekday::year_month_weekday(const sys_days& dp) NOEXCEPT
+    : year_month_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_weekday::year_month_weekday(const local_days& dp) NOEXCEPT
+    : year_month_weekday(from_days(dp.time_since_epoch()))
+    {}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday&
+year_month_weekday::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_weekday::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_weekday::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday
+year_month_weekday::weekday() const NOEXCEPT
+{
+    return wdi_.weekday();
+}
+
+CONSTCD11
+inline
+unsigned
+year_month_weekday::index() const NOEXCEPT
+{
+    return wdi_.index();
+}
+
+CONSTCD11
+inline
+weekday_indexed
+year_month_weekday::weekday_indexed() const NOEXCEPT
+{
+    return wdi_;
+}
+
+CONSTCD14
+inline
+year_month_weekday::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_weekday::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD14
+inline
+bool
+year_month_weekday::ok() const NOEXCEPT
+{
+    if (!y_.ok() || !m_.ok() || !wdi_.weekday().ok() || wdi_.index() < 1)
+        return false;
+    if (wdi_.index() <= 4)
+        return true;
+    auto d2 = wdi_.weekday() - julian::weekday(y_/m_/1) + days((wdi_.index()-1)*7 + 1);
+    return static_cast<unsigned>(d2.count()) <= static_cast<unsigned>((y_/m_/last).day());
+}
+
+CONSTCD14
+inline
+year_month_weekday
+year_month_weekday::from_days(days d) NOEXCEPT
+{
+    sys_days dp{d};
+    auto const wd = julian::weekday(dp);
+    auto const ymd = year_month_day(dp);
+    return {ymd.year(), ymd.month(), wd[(static_cast<unsigned>(ymd.day())-1)/7+1]};
+}
+
+CONSTCD14
+inline
+days
+year_month_weekday::to_days() const NOEXCEPT
+{
+    auto d = sys_days(y_/m_/1);
+    return (d + (wdi_.weekday() - julian::weekday(d) + days{(wdi_.index()-1)*7})
+           ).time_since_epoch();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() &&
+           x.weekday_indexed() == y.weekday_indexed();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_weekday& x, const year_month_weekday& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday& ymwdi)
+{
+    return os << ymwdi.year() << '/' << ymwdi.month()
+              << '/' << ymwdi.weekday_indexed();
+}
+
+CONSTCD14
+inline
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const months& dm) NOEXCEPT
+{
+    return (ymwd.year() / ymwd.month() + dm) / ymwd.weekday_indexed();
+}
+
+CONSTCD14
+inline
+year_month_weekday
+operator+(const months& dm, const year_month_weekday& ymwd) NOEXCEPT
+{
+    return ymwd + dm;
+}
+
+CONSTCD14
+inline
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const months& dm) NOEXCEPT
+{
+    return ymwd + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator+(const year_month_weekday& ymwd, const years& dy) NOEXCEPT
+{
+    return {ymwd.year()+dy, ymwd.month(), ymwd.weekday_indexed()};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator+(const years& dy, const year_month_weekday& ymwd) NOEXCEPT
+{
+    return ymwd + dy;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator-(const year_month_weekday& ymwd, const years& dy) NOEXCEPT
+{
+    return ymwd + (-dy);
+}
+
+// year_month_weekday_last
+
+CONSTCD11
+inline
+year_month_weekday_last::year_month_weekday_last(const julian::year& y,
+                                                 const julian::month& m,
+                                                 const julian::weekday_last& wdl) NOEXCEPT
+    : y_(y)
+    , m_(m)
+    , wdl_(wdl)
+    {}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator+=(const months& m) NOEXCEPT
+{
+    *this = *this + m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator-=(const months& m) NOEXCEPT
+{
+    *this = *this - m;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator+=(const years& y) NOEXCEPT
+{
+    *this = *this + y;
+    return *this;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last&
+year_month_weekday_last::operator-=(const years& y) NOEXCEPT
+{
+    *this = *this - y;
+    return *this;
+}
+
+CONSTCD11 inline year year_month_weekday_last::year() const NOEXCEPT {return y_;}
+CONSTCD11 inline month year_month_weekday_last::month() const NOEXCEPT {return m_;}
+
+CONSTCD11
+inline
+weekday
+year_month_weekday_last::weekday() const NOEXCEPT
+{
+    return wdl_.weekday();
+}
+
+CONSTCD11
+inline
+weekday_last
+year_month_weekday_last::weekday_last() const NOEXCEPT
+{
+    return wdl_;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last::operator sys_days() const NOEXCEPT
+{
+    return sys_days{to_days()};
+}
+
+CONSTCD14
+inline
+year_month_weekday_last::operator local_days() const NOEXCEPT
+{
+    return local_days{to_days()};
+}
+
+CONSTCD11
+inline
+bool
+year_month_weekday_last::ok() const NOEXCEPT
+{
+    return y_.ok() && m_.ok() && wdl_.ok();
+}
+
+CONSTCD14
+inline
+days
+year_month_weekday_last::to_days() const NOEXCEPT
+{
+    auto const d = sys_days(y_/m_/last);
+    return (d - (julian::weekday{d} - wdl_.weekday())).time_since_epoch();
+}
+
+CONSTCD11
+inline
+bool
+operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT
+{
+    return x.year() == y.year() && x.month() == y.month() &&
+           x.weekday_last() == y.weekday_last();
+}
+
+CONSTCD11
+inline
+bool
+operator!=(const year_month_weekday_last& x, const year_month_weekday_last& y) NOEXCEPT
+{
+    return !(x == y);
+}
+
+template<class CharT, class Traits>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const year_month_weekday_last& ymwdl)
+{
+    return os << ymwdl.year() << '/' << ymwdl.month() << '/' << ymwdl.weekday_last();
+}
+
+CONSTCD14
+inline
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT
+{
+    return (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last();
+}
+
+CONSTCD14
+inline
+year_month_weekday_last
+operator+(const months& dm, const year_month_weekday_last& ymwdl) NOEXCEPT
+{
+    return ymwdl + dm;
+}
+
+CONSTCD14
+inline
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const months& dm) NOEXCEPT
+{
+    return ymwdl + (-dm);
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator+(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT
+{
+    return {ymwdl.year()+dy, ymwdl.month(), ymwdl.weekday_last()};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator+(const years& dy, const year_month_weekday_last& ymwdl) NOEXCEPT
+{
+    return ymwdl + dy;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator-(const year_month_weekday_last& ymwdl, const years& dy) NOEXCEPT
+{
+    return ymwdl + (-dy);
+}
+
+// year_month from operator/()
+
+CONSTCD11
+inline
+year_month
+operator/(const year& y, const month& m) NOEXCEPT
+{
+    return {y, m};
+}
+
+CONSTCD11
+inline
+year_month
+operator/(const year& y, int   m) NOEXCEPT
+{
+    return y / month(static_cast<unsigned>(m));
+}
+
+// month_day from operator/()
+
+CONSTCD11
+inline
+month_day
+operator/(const month& m, const day& d) NOEXCEPT
+{
+    return {m, d};
+}
+
+CONSTCD11
+inline
+month_day
+operator/(const day& d, const month& m) NOEXCEPT
+{
+    return m / d;
+}
+
+CONSTCD11
+inline
+month_day
+operator/(const month& m, int d) NOEXCEPT
+{
+    return m / day(static_cast<unsigned>(d));
+}
+
+CONSTCD11
+inline
+month_day
+operator/(int m, const day& d) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / d;
+}
+
+CONSTCD11 inline month_day operator/(const day& d, int m) NOEXCEPT {return m / d;}
+
+// month_day_last from operator/()
+
+CONSTCD11
+inline
+month_day_last
+operator/(const month& m, last_spec) NOEXCEPT
+{
+    return month_day_last{m};
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(last_spec, const month& m) NOEXCEPT
+{
+    return m/last;
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(int m, last_spec) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m))/last;
+}
+
+CONSTCD11
+inline
+month_day_last
+operator/(last_spec, int m) NOEXCEPT
+{
+    return m/last;
+}
+
+// month_weekday from operator/()
+
+CONSTCD11
+inline
+month_weekday
+operator/(const month& m, const weekday_indexed& wdi) NOEXCEPT
+{
+    return {m, wdi};
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(const weekday_indexed& wdi, const month& m) NOEXCEPT
+{
+    return m / wdi;
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(int m, const weekday_indexed& wdi) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / wdi;
+}
+
+CONSTCD11
+inline
+month_weekday
+operator/(const weekday_indexed& wdi, int m) NOEXCEPT
+{
+    return m / wdi;
+}
+
+// month_weekday_last from operator/()
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const month& m, const weekday_last& wdl) NOEXCEPT
+{
+    return {m, wdl};
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const weekday_last& wdl, const month& m) NOEXCEPT
+{
+    return m / wdl;
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(int m, const weekday_last& wdl) NOEXCEPT
+{
+    return month(static_cast<unsigned>(m)) / wdl;
+}
+
+CONSTCD11
+inline
+month_weekday_last
+operator/(const weekday_last& wdl, int m) NOEXCEPT
+{
+    return m / wdl;
+}
+
+// year_month_day from operator/()
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year_month& ym, const day& d) NOEXCEPT
+{
+    return {ym.year(), ym.month(), d};
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year_month& ym, int d)  NOEXCEPT
+{
+    return ym / day(static_cast<unsigned>(d));
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const year& y, const month_day& md) NOEXCEPT
+{
+    return y / md.month() / md.day();
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(int y, const month_day& md) NOEXCEPT
+{
+    return year(y) / md;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const month_day& md, const year& y)  NOEXCEPT
+{
+    return y / md;
+}
+
+CONSTCD11
+inline
+year_month_day
+operator/(const month_day& md, int y) NOEXCEPT
+{
+    return year(y) / md;
+}
+
+// year_month_day_last from operator/()
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const year_month& ym, last_spec) NOEXCEPT
+{
+    return {ym.year(), month_day_last{ym.month()}};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const year& y, const month_day_last& mdl) NOEXCEPT
+{
+    return {y, mdl};
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(int y, const month_day_last& mdl) NOEXCEPT
+{
+    return year(y) / mdl;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const month_day_last& mdl, const year& y) NOEXCEPT
+{
+    return y / mdl;
+}
+
+CONSTCD11
+inline
+year_month_day_last
+operator/(const month_day_last& mdl, int y) NOEXCEPT
+{
+    return year(y) / mdl;
+}
+
+// year_month_weekday from operator/()
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const year_month& ym, const weekday_indexed& wdi) NOEXCEPT
+{
+    return {ym.year(), ym.month(), wdi};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const year& y, const month_weekday& mwd) NOEXCEPT
+{
+    return {y, mwd.month(), mwd.weekday_indexed()};
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(int y, const month_weekday& mwd) NOEXCEPT
+{
+    return year(y) / mwd;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const month_weekday& mwd, const year& y) NOEXCEPT
+{
+    return y / mwd;
+}
+
+CONSTCD11
+inline
+year_month_weekday
+operator/(const month_weekday& mwd, int y) NOEXCEPT
+{
+    return year(y) / mwd;
+}
+
+// year_month_weekday_last from operator/()
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const year_month& ym, const weekday_last& wdl) NOEXCEPT
+{
+    return {ym.year(), ym.month(), wdl};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const year& y, const month_weekday_last& mwdl) NOEXCEPT
+{
+    return {y, mwdl.month(), mwdl.weekday_last()};
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(int y, const month_weekday_last& mwdl) NOEXCEPT
+{
+    return year(y) / mwdl;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, const year& y) NOEXCEPT
+{
+    return y / mwdl;
+}
+
+CONSTCD11
+inline
+year_month_weekday_last
+operator/(const month_weekday_last& mwdl, int y) NOEXCEPT
+{
+    return year(y) / mwdl;
+}
+
+}  // namespace julian
+
+#endif  // JULIAN_H
diff --git a/src/libs/date/includes/date/ptz.h b/src/libs/date/includes/date/ptz.h
new file mode 100644
index 00000000..6ff1ab9b
--- /dev/null
+++ b/src/libs/date/includes/date/ptz.h
@@ -0,0 +1,627 @@
+#ifndef PTZ_H
+#define PTZ_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2017 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// This header allows Posix-style time zones as specified for TZ here:
+// http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
+//
+// Posix::time_zone can be constructed with a posix-style string and then used in
+// a zoned_time like so:
+//
+// zoned_time<system_clock::duration, Posix::time_zone> zt{"EST5EDT,M3.2.0,M11.1.0",
+//                                                         system_clock::now()};
+// or:
+//
+// Posix::time_zone tz{"EST5EDT,M3.2.0,M11.1.0"};
+// zoned_time<system_clock::duration, Posix::time_zone> zt{tz, system_clock::now()};
+//
+// Note, Posix-style time zones are not recommended for all of the reasons described here:
+// https://stackoverflow.com/tags/timezone/info
+//
+// They are provided here as a non-trivial custom time zone example, and if you really
+// have to have Posix time zones, you're welcome to use this one.
+
+#include "date/tz.h"
+#include <cctype>
+#include <ostream>
+#include <string>
+
+namespace Posix
+{
+
+namespace detail
+{
+
+#if HAS_STRING_VIEW
+
+using string_t = std::string_view;
+
+#else  // !HAS_STRING_VIEW
+
+using string_t = std::string;
+
+#endif  // !HAS_STRING_VIEW
+
+class rule;
+
+void throw_invalid(const string_t& s, unsigned i, const string_t& message);
+unsigned read_date(const string_t& s, unsigned i, rule& r);
+unsigned read_name(const string_t& s, unsigned i, std::string& name);
+unsigned read_signed_time(const string_t& s, unsigned i, std::chrono::seconds& t);
+unsigned read_unsigned_time(const string_t& s, unsigned i, std::chrono::seconds& t);
+unsigned read_unsigned(const string_t& s, unsigned i,  unsigned limit, unsigned& u);
+
+class rule
+{
+    enum {off, J, M, N};
+
+    date::month m_;
+    date::weekday wd_;
+    unsigned short n_    : 14;
+    unsigned short mode_ : 2;
+    std::chrono::duration<std::int32_t> time_ = std::chrono::hours{2};
+
+public:
+    rule() : mode_(off) {}
+
+    bool ok() const {return mode_ != off;}
+    date::local_seconds operator()(date::year y) const;
+
+    friend std::ostream& operator<<(std::ostream& os, const rule& r);
+    friend unsigned read_date(const string_t& s, unsigned i, rule& r);
+};
+
+inline
+date::local_seconds
+rule::operator()(date::year y) const
+{
+    using date::local_days;
+    using date::January;
+    using date::days;
+    using date::last;
+    using sec = std::chrono::seconds;
+    date::local_seconds t;
+    switch (mode_)
+    {
+    case J:
+        t = local_days{y/January/0} + days{n_ + (y.is_leap() && n_ > 59)} + sec{time_};
+        break;
+    case M:
+        t = (n_ == 5 ? local_days{y/m_/wd_[last]} : local_days{y/m_/wd_[n_]}) + sec{time_};
+        break;
+    case N:
+        t = local_days{y/January/1} + days{n_} + sec{time_};
+        break;
+    default:
+        assert(!"rule called with bad mode");
+    }
+    return t;
+}
+
+inline
+std::ostream&
+operator<<(std::ostream& os, const rule& r)
+{
+    switch (r.mode_)
+    {
+    case rule::J:
+        os << 'J' << r.n_ << date::format(" %T", r.time_);
+        break;
+    case rule::M:
+        if (r.n_ == 5)
+            os << r.m_/r.wd_[date::last];
+        else
+            os << r.m_/r.wd_[r.n_];
+        os <<  date::format(" %T", r.time_);
+        break;
+    case rule::N:
+        os << r.n_ << date::format(" %T", r.time_);
+        break;
+    default:
+        break;
+    }
+    return os;
+}
+
+}  // namespace detail
+
+class time_zone
+{
+    std::string          std_abbrev_;
+    std::string          dst_abbrev_ = {};
+    std::chrono::seconds offset_;
+    std::chrono::seconds save_ = std::chrono::hours{1};
+    detail::rule         start_rule_;
+    detail::rule         end_rule_;
+
+public:
+    explicit time_zone(const detail::string_t& name);
+
+    template <class Duration>
+        date::sys_info   get_info(date::sys_time<Duration> st) const;
+    template <class Duration>
+        date::local_info get_info(date::local_time<Duration> tp) const;
+
+    template <class Duration>
+        date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys(date::local_time<Duration> tp) const;
+
+    template <class Duration>
+        date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys(date::local_time<Duration> tp, date::choose z) const;
+
+    template <class Duration>
+        date::local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_local(date::sys_time<Duration> tp) const;
+
+    friend std::ostream& operator<<(std::ostream& os, const time_zone& z);
+
+    const time_zone* operator->() const {return this;}
+};
+
+inline
+time_zone::time_zone(const detail::string_t& s)
+{
+    using detail::read_name;
+    using detail::read_signed_time;
+    using detail::throw_invalid;
+    auto i = read_name(s, 0, std_abbrev_);
+    i = read_signed_time(s, i, offset_);
+    offset_ = -offset_;
+    if (i != s.size())
+    {
+        i = read_name(s, i, dst_abbrev_);
+        if (i != s.size())
+        {
+            if (s[i] != ',')
+                i = read_signed_time(s, i, save_);
+            if (i != s.size())
+            {
+                if (s[i] != ',')
+                    throw_invalid(s, i, "Expecting end of string or ',' to start rule");
+                ++i;
+                i = read_date(s, i, start_rule_);
+                if (i == s.size() || s[i] != ',')
+                    throw_invalid(s, i, "Expecting ',' and then the ending rule");
+                ++i;
+                i = read_date(s, i, end_rule_);
+                if (i != s.size())
+                    throw_invalid(s, i, "Found unexpected trailing characters");
+            }
+        }
+    }
+}
+
+template <class Duration>
+date::sys_info
+time_zone::get_info(date::sys_time<Duration> st) const
+{
+    using date::sys_info;
+    using date::year_month_day;
+    using date::sys_seconds;
+    using date::sys_days;
+    using date::floor;
+    using date::ceil;
+    using date::days;
+    using date::years;
+    using date::year;
+    using date::January;
+    using date::December;
+    using date::last;
+    using std::chrono::minutes;
+    sys_info r{};
+    r.offset = offset_;
+    if (start_rule_.ok())
+    {
+        auto y = year_month_day{floor<days>(st)}.year();
+        auto start = sys_seconds{(start_rule_(y) - offset_).time_since_epoch()};
+        auto end   = sys_seconds{(end_rule_(y) - (offset_ + save_)).time_since_epoch()};
+        if (start <= st && st < end)
+        {
+            r.begin = start;
+            r.end = end;
+            r.offset += save_;
+            r.save = ceil<minutes>(save_);
+            r.abbrev = dst_abbrev_;
+        }
+        else if (st < start)
+        {
+            r.begin = sys_seconds{(end_rule_(y-years{1}) -
+                                   (offset_ + save_)).time_since_epoch()};
+            r.end = start;
+            r.abbrev = std_abbrev_;
+        }
+        else  // st >= end
+        {
+            r.begin = end;
+            r.end = sys_seconds{(start_rule_(y+years{1}) - offset_).time_since_epoch()};
+            r.abbrev = std_abbrev_;
+        }
+    }
+    else  //  constant offset
+    {
+        r.begin = sys_days{year::min()/January/1};
+        r.end   = sys_days{year::max()/December/last};
+        r.abbrev = std_abbrev_;
+    }
+    return r;
+}
+
+template <class Duration>
+date::local_info
+time_zone::get_info(date::local_time<Duration> tp) const
+{
+    using date::local_info;
+    using date::year_month_day;
+    using date::days;
+    using date::sys_days;
+    using date::sys_seconds;
+    using date::years;
+    using date::year;
+    using date::ceil;
+    using date::January;
+    using date::December;
+    using date::last;
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    local_info r{};
+    using date::floor;
+    if (start_rule_.ok())
+    {
+        auto y = year_month_day{floor<days>(tp)}.year();
+        auto start = sys_seconds{(start_rule_(y) - offset_).time_since_epoch()};
+        auto end   = sys_seconds{(end_rule_(y) - (offset_ + save_)).time_since_epoch()};
+        auto utcs = sys_seconds{floor<seconds>(tp - offset_).time_since_epoch()};
+        auto utcd = sys_seconds{floor<seconds>(tp - (offset_ + save_)).time_since_epoch()};
+        if ((utcs < start) != (utcd < start))
+        {
+            r.first.begin = sys_seconds{(end_rule_(y-years{1}) -
+                                         (offset_ + save_)).time_since_epoch()};
+            r.first.end = start;
+            r.first.offset = offset_;
+            r.first.abbrev = std_abbrev_;
+            r.second.begin = start;
+            r.second.end = end;
+            r.second.abbrev = dst_abbrev_;
+            r.second.offset = offset_ + save_;
+            r.second.save = ceil<minutes>(save_);
+            r.result = save_ > seconds{0} ? local_info::nonexistent
+                                          : local_info::ambiguous;
+        }
+        else if ((utcs < end) != (utcd < end))
+        {
+            r.first.begin = start;
+            r.first.end = end;
+            r.first.offset = offset_ + save_;
+            r.first.save = ceil<minutes>(save_);
+            r.first.abbrev = dst_abbrev_;
+            r.second.begin = end;
+            r.second.end = sys_seconds{(start_rule_(y+years{1}) -
+                                        offset_).time_since_epoch()};
+            r.second.abbrev = std_abbrev_;
+            r.second.offset = offset_;
+            r.result = save_ > seconds{0} ? local_info::ambiguous
+                                          : local_info::nonexistent;
+        }
+        else if (utcs < start)
+        {
+            r.first.begin = sys_seconds{(end_rule_(y-years{1}) -
+                                   (offset_ + save_)).time_since_epoch()};
+            r.first.end = start;
+            r.first.offset = offset_;
+            r.first.abbrev = std_abbrev_;
+        }
+        else if (utcs < end)
+        {
+            r.first.begin = start;
+            r.first.end = end;
+            r.first.offset = offset_ + save_;
+            r.first.save = ceil<minutes>(save_);
+            r.first.abbrev = dst_abbrev_;
+        }
+        else
+        {
+            r.first.begin = end;
+            r.first.end = sys_seconds{(start_rule_(y+years{1}) -
+                                       offset_).time_since_epoch()};
+            r.first.abbrev = std_abbrev_;
+            r.first.offset = offset_;
+        }
+    }
+    else  //  constant offset
+    {
+        r.first.begin = sys_days{year::min()/January/1};
+        r.first.end   = sys_days{year::max()/December/last};
+        r.first.abbrev = std_abbrev_;
+        r.first.offset = offset_;
+    }
+    return r;
+}
+
+template <class Duration>
+date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys(date::local_time<Duration> tp) const
+{
+    using date::local_info;
+    using date::sys_time;
+    using date::ambiguous_local_time;
+    auto i = get_info(tp);
+    if (i.result == local_info::nonexistent)
+        throw nonexistent_local_time(tp, i);
+    else if (i.result == local_info::ambiguous)
+        throw ambiguous_local_time(tp, i);
+    return sys_time<Duration>{tp.time_since_epoch()} - i.first.offset;
+}
+
+template <class Duration>
+date::sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys(date::local_time<Duration> tp, date::choose z) const
+{
+    using date::local_info;
+    using date::sys_time;
+    using date::choose;
+    auto i = get_info(tp);
+    if (i.result == local_info::nonexistent)
+    {
+        return i.first.end;
+    }
+    else if (i.result == local_info::ambiguous)
+    {
+        if (z == choose::latest)
+            return sys_time<Duration>{tp.time_since_epoch()} - i.second.offset;
+    }
+    return sys_time<Duration>{tp.time_since_epoch()} - i.first.offset;
+}
+
+template <class Duration>
+date::local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_local(date::sys_time<Duration> tp) const
+{
+    using date::local_time;
+    using std::chrono::seconds;
+    using LT = local_time<typename std::common_type<Duration, seconds>::type>;
+    auto i = get_info(tp);
+    return LT{(tp + i.offset).time_since_epoch()};
+}
+
+inline
+std::ostream&
+operator<<(std::ostream& os, const time_zone& z)
+{
+    using date::operator<<;
+    os << '{';
+    os << z.std_abbrev_ << ", " << z.dst_abbrev_ << date::format(", %T, ", z.offset_)
+       << date::format("%T, [", z.save_) << z.start_rule_ << ", " << z.end_rule_ << ")}";
+    return os;
+}
+
+namespace detail
+{
+
+inline
+void
+throw_invalid(const string_t& s, unsigned i, const string_t& message)
+{
+    throw std::runtime_error(std::string("Invalid time_zone initializer.\n") +
+                             std::string(message) + ":\n" +
+                             std::string(s) + '\n' +
+                             "\x1b[1;32m" +
+                             std::string(i, '~') + '^' +
+                             std::string(s.size()-i-1, '~') +
+                             "\x1b[0m");
+}
+
+inline
+unsigned
+read_date(const string_t& s, unsigned i, rule& r)
+{
+    using date::month;
+    using date::weekday;
+    if (i == s.size())
+        throw_invalid(s, i, "Expected rule but found end of string");
+    if (s[i] == 'J')
+    {
+        ++i;
+        unsigned n;
+        i = read_unsigned(s, i, 3, n);
+        r.mode_ = rule::J;
+        r.n_ = n;
+    }
+    else if (s[i] == 'M')
+    {
+        ++i;
+        unsigned m;
+        i = read_unsigned(s, i, 2, m);
+        if (i == s.size() || s[i] != '.')
+            throw_invalid(s, i, "Expected '.' after month");
+        ++i;
+        unsigned n;
+        i = read_unsigned(s, i, 1, n);
+        if (i == s.size() || s[i] != '.')
+            throw_invalid(s, i, "Expected '.' after weekday index");
+        ++i;
+        unsigned wd;
+        i = read_unsigned(s, i, 1, wd);
+        r.mode_ = rule::M;
+        r.m_ = month{m};
+        r.wd_ = weekday{wd};
+        r.n_ = n;
+    }
+    else if (std::isdigit(s[i]))
+    {
+        unsigned n;
+        i = read_unsigned(s, i, 3, n);
+        r.mode_ = rule::N;
+        r.n_ = n;
+    }
+    else
+        throw_invalid(s, i, "Expected 'J', 'M', or a digit to start rule");
+    if (i != s.size() && s[i] == '/')
+    {
+        ++i;
+        std::chrono::seconds t;
+        i = read_unsigned_time(s, i, t);
+        r.time_ = t;
+    }
+    return i;
+}
+
+inline
+unsigned
+read_name(const string_t& s, unsigned i, std::string& name)
+{
+    if (i == s.size())
+        throw_invalid(s, i, "Expected a name but found end of string");
+    if (s[i] == '<')
+    {
+        ++i;
+        while (true)
+        {
+            if (i == s.size())
+                throw_invalid(s, i,
+                              "Expected to find closing '>', but found end of string");
+            if (s[i] == '>')
+                break;
+            name.push_back(s[i]);
+            ++i;
+        }
+        ++i;
+    }
+    else
+    {
+        while (i != s.size() && std::isalpha(s[i]))
+        {
+            name.push_back(s[i]);
+            ++i;
+        }
+    }
+    if (name.size() < 3)
+        throw_invalid(s, i, "Found name to be shorter than 3 characters");
+    return i;
+}
+
+inline
+unsigned
+read_signed_time(const string_t& s, unsigned i,
+                                  std::chrono::seconds& t)
+{
+    if (i == s.size())
+        throw_invalid(s, i, "Expected to read signed time, but found end of string");
+    bool negative = false;
+    if (s[i] == '-')
+    {
+        negative = true;
+        ++i;
+    }
+    else if (s[i] == '+')
+        ++i;
+    i = read_unsigned_time(s, i, t);
+    if (negative)
+        t = -t;
+    return i;
+}
+
+inline
+unsigned
+read_unsigned_time(const string_t& s, unsigned i, std::chrono::seconds& t)
+{
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    using std::chrono::hours;
+    if (i == s.size())
+        throw_invalid(s, i, "Expected to read unsigned time, but found end of string");
+    unsigned x;
+    i = read_unsigned(s, i, 2, x);
+    t = hours{x};
+    if (i != s.size() && s[i] == ':')
+    {
+        ++i;
+        i = read_unsigned(s, i, 2, x);
+        t += minutes{x};
+        if (i != s.size() && s[i] == ':')
+        {
+            ++i;
+            i = read_unsigned(s, i, 2, x);
+            t += seconds{x};
+        }
+    }
+    return i;
+}
+
+inline
+unsigned
+read_unsigned(const string_t& s, unsigned i, unsigned limit, unsigned& u)
+{
+    if (i == s.size() || !std::isdigit(s[i]))
+        throw_invalid(s, i, "Expected to find a decimal digit");
+    u = static_cast<unsigned>(s[i] - '0');
+    unsigned count = 1;
+    for (++i; count < limit && i != s.size() && std::isdigit(s[i]); ++i, ++count)
+        u = u * 10 + static_cast<unsigned>(s[i] - '0');
+    return i;
+}
+
+}  // namespace detail
+
+}  // namespace Posix
+
+namespace date
+{
+
+template <>
+struct zoned_traits<Posix::time_zone>
+{
+
+#if HAS_STRING_VIEW
+
+    static
+    Posix::time_zone
+    locate_zone(std::string_view name)
+    {
+        return Posix::time_zone{name};
+    }
+
+#else  // !HAS_STRING_VIEW
+
+    static
+    Posix::time_zone
+    locate_zone(const std::string& name)
+    {
+        return Posix::time_zone{name};
+    }
+
+    static
+    Posix::time_zone
+    locate_zone(const char* name)
+    {
+        return Posix::time_zone{name};
+    }
+
+#endif  // !HAS_STRING_VIEW
+
+};
+
+}  // namespace date
+
+#endif  // PTZ_H
diff --git a/src/libs/date/includes/date/tz.h b/src/libs/date/includes/date/tz.h
new file mode 100644
index 00000000..22eac555
--- /dev/null
+++ b/src/libs/date/includes/date/tz.h
@@ -0,0 +1,2775 @@
+#ifndef TZ_H
+#define TZ_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2015, 2016, 2017 Howard Hinnant
+// Copyright (c) 2017 Jiangang Zhuang
+// Copyright (c) 2017 Aaron Bishop
+// Copyright (c) 2017 Tomasz Kamiński
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+// Get more recent database at http://www.iana.org/time-zones
+
+// The notion of "current timezone" is something the operating system is expected to "just
+// know". How it knows this is system specific. It's often a value set by the user at OS
+// installation time and recorded by the OS somewhere. On Linux and Mac systems the current
+// timezone name is obtained by looking at the name or contents of a particular file on
+// disk. On Windows the current timezone name comes from the registry. In either method,
+// there is no guarantee that the "native" current timezone name obtained will match any
+// of the "Standard" names in this library's "database". On Linux, the names usually do
+// seem to match so mapping functions to map from native to "Standard" are typically not
+// required. On Windows, the names are never "Standard" so mapping is always required.
+// Technically any OS may use the mapping process but currently only Windows does use it.
+
+#ifndef USE_OS_TZDB
+#  define USE_OS_TZDB 0
+#endif
+
+#ifndef HAS_REMOTE_API
+#  if USE_OS_TZDB == 0
+#    ifdef _WIN32
+#      define HAS_REMOTE_API 0
+#    else
+#      define HAS_REMOTE_API 1
+#    endif
+#  else  // HAS_REMOTE_API makes no since when using the OS timezone database
+#    define HAS_REMOTE_API 0
+#  endif
+#endif
+
+#ifdef __clang__
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wconstant-logical-operand"
+#endif
+
+static_assert(!(USE_OS_TZDB && HAS_REMOTE_API),
+              "USE_OS_TZDB and HAS_REMOTE_API can not be used together");
+
+#ifdef __clang__
+# pragma clang diagnostic pop
+#endif
+
+#ifndef AUTO_DOWNLOAD
+#  define AUTO_DOWNLOAD HAS_REMOTE_API
+#endif
+
+static_assert(HAS_REMOTE_API == 0 ? AUTO_DOWNLOAD == 0 : true,
+              "AUTO_DOWNLOAD can not be turned on without HAS_REMOTE_API");
+
+#ifndef USE_SHELL_API
+#  define USE_SHELL_API 1
+#endif
+
+#if USE_OS_TZDB
+#  ifdef _WIN32
+#    error "USE_OS_TZDB can not be used on Windows"
+#  endif
+#  ifndef MISSING_LEAP_SECONDS
+#    ifdef __APPLE__
+#      define MISSING_LEAP_SECONDS 1
+#    else
+#      define MISSING_LEAP_SECONDS 0
+#    endif
+#  endif
+#else
+#  define MISSING_LEAP_SECONDS 0
+#endif
+
+#ifndef HAS_DEDUCTION_GUIDES
+#  if __cplusplus >= 201703
+#    define HAS_DEDUCTION_GUIDES 1
+#  else
+#    define HAS_DEDUCTION_GUIDES 0
+#  endif
+#endif  // HAS_DEDUCTION_GUIDES
+
+#include "date.h"
+
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#include "tz_private.h"
+#endif
+
+#include <algorithm>
+#include <atomic>
+#include <cassert>
+#include <chrono>
+#include <istream>
+#include <locale>
+#include <memory>
+#include <mutex>
+#include <ostream>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#ifdef _WIN32
+#  ifdef DATE_BUILD_DLL
+#    define DATE_API __declspec(dllexport)
+#  elif defined(DATE_USE_DLL)
+#    define DATE_API __declspec(dllimport)
+#  else
+#    define DATE_API
+#  endif
+#else
+#  ifdef DATE_BUILD_DLL
+#    define DATE_API __attribute__ ((visibility ("default")))
+#  else
+#    define DATE_API
+#  endif
+#endif
+
+namespace date
+{
+
+enum class choose {earliest, latest};
+
+namespace detail
+{
+    struct undocumented;
+
+    template<typename T>
+    struct nodeduct
+    {
+       using type = T;
+    };
+
+    template<typename T>
+    using nodeduct_t = typename nodeduct<T>::type;
+}
+
+struct sys_info
+{
+    sys_seconds          begin;
+    sys_seconds          end;
+    std::chrono::seconds offset;
+    std::chrono::minutes save;
+    std::string          abbrev;
+};
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const sys_info& r)
+{
+    os << r.begin << '\n';
+    os << r.end << '\n';
+    os << make_time(r.offset) << "\n";
+    os << make_time(r.save) << "\n";
+    os << r.abbrev << '\n';
+    return os;
+}
+
+struct local_info
+{
+    enum {unique, nonexistent, ambiguous} result;
+    sys_info first;
+    sys_info second;
+};
+
+template<class CharT, class Traits>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const local_info& r)
+{
+    if (r.result == local_info::nonexistent)
+        os << "nonexistent between\n";
+    else if (r.result == local_info::ambiguous)
+        os << "ambiguous between\n";
+    os << r.first;
+    if (r.result != local_info::unique)
+    {
+        os << "and\n";
+        os << r.second;
+    }
+    return os;
+}
+
+class nonexistent_local_time
+    : public std::runtime_error
+{
+public:
+    template <class Duration>
+        nonexistent_local_time(local_time<Duration> tp, const local_info& i);
+
+private:
+    template <class Duration>
+    static
+    std::string
+    make_msg(local_time<Duration> tp, const local_info& i);
+};
+
+template <class Duration>
+inline
+nonexistent_local_time::nonexistent_local_time(local_time<Duration> tp,
+                                               const local_info& i)
+    : std::runtime_error(make_msg(tp, i))
+{
+}
+
+template <class Duration>
+std::string
+nonexistent_local_time::make_msg(local_time<Duration> tp, const local_info& i)
+{
+    assert(i.result == local_info::nonexistent);
+    std::ostringstream os;
+    os << tp << " is in a gap between\n"
+       << local_seconds{i.first.end.time_since_epoch()} + i.first.offset << ' '
+       << i.first.abbrev << " and\n"
+       << local_seconds{i.second.begin.time_since_epoch()} + i.second.offset << ' '
+       << i.second.abbrev
+       << " which are both equivalent to\n"
+       << i.first.end << " UTC";
+    return os.str();
+}
+
+class ambiguous_local_time
+    : public std::runtime_error
+{
+public:
+    template <class Duration>
+        ambiguous_local_time(local_time<Duration> tp, const local_info& i);
+
+private:
+    template <class Duration>
+    static
+    std::string
+    make_msg(local_time<Duration> tp, const local_info& i);
+};
+
+template <class Duration>
+inline
+ambiguous_local_time::ambiguous_local_time(local_time<Duration> tp, const local_info& i)
+    : std::runtime_error(make_msg(tp, i))
+{
+}
+
+template <class Duration>
+std::string
+ambiguous_local_time::make_msg(local_time<Duration> tp, const local_info& i)
+{
+    assert(i.result == local_info::ambiguous);
+    std::ostringstream os;
+    os << tp << " is ambiguous.  It could be\n"
+       << tp << ' ' << i.first.abbrev << " == "
+       << tp - i.first.offset << " UTC or\n"
+       << tp << ' ' << i.second.abbrev  << " == "
+       << tp - i.second.offset  << " UTC";
+    return os.str();
+}
+
+class time_zone;
+
+#if HAS_STRING_VIEW
+DATE_API const time_zone* locate_zone(std::string_view tz_name);
+#else
+DATE_API const time_zone* locate_zone(const std::string& tz_name);
+#endif
+
+DATE_API const time_zone* current_zone();
+
+template <class T>
+struct zoned_traits
+{
+};
+
+template <>
+struct zoned_traits<const time_zone*>
+{
+    static
+    const time_zone*
+    default_zone()
+    {
+        return date::locate_zone("Etc/UTC");
+    }
+
+#if HAS_STRING_VIEW
+
+    static
+    const time_zone*
+    locate_zone(std::string_view name)
+    {
+        return date::locate_zone(name);
+    }
+
+#else  // !HAS_STRING_VIEW
+
+    static
+    const time_zone*
+    locate_zone(const std::string& name)
+    {
+        return date::locate_zone(name);
+    }
+
+    static
+    const time_zone*
+    locate_zone(const char* name)
+    {
+        return date::locate_zone(name);
+    }
+
+#endif  // !HAS_STRING_VIEW
+};
+
+template <class Duration, class TimeZonePtr>
+class zoned_time;
+
+template <class Duration1, class Duration2, class TimeZonePtr>
+bool
+operator==(const zoned_time<Duration1, TimeZonePtr>& x,
+           const zoned_time<Duration2, TimeZonePtr>& y);
+
+template <class Duration, class TimeZonePtr = const time_zone*>
+class zoned_time
+{
+public:
+    using duration = typename std::common_type<Duration, std::chrono::seconds>::type;
+
+private:
+    TimeZonePtr        zone_;
+    sys_time<duration> tp_;
+
+public:
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = decltype(zoned_traits<T>::default_zone())>
+#endif
+        zoned_time();
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = decltype(zoned_traits<T>::default_zone())>
+#endif
+        zoned_time(const sys_time<Duration>& st);
+    explicit zoned_time(TimeZonePtr z);
+
+#if HAS_STRING_VIEW
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string_view()))
+                  >::value
+              >::type>
+        explicit zoned_time(std::string_view name);
+#else
+#  if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string()))
+                  >::value
+              >::type>
+#  endif
+        explicit zoned_time(const std::string& name);
+#endif
+
+    template <class Duration2,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value
+                      >::type>
+        zoned_time(const zoned_time<Duration2, TimeZonePtr>& zt) NOEXCEPT;
+
+    zoned_time(TimeZonePtr z, const sys_time<Duration>& st);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_convertible
+                  <
+                      decltype(std::declval<T&>()->to_sys(local_time<Duration>{})),
+                      sys_time<duration>
+                  >::value
+              >::type>
+#endif
+        zoned_time(TimeZonePtr z, const local_time<Duration>& tp);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_convertible
+                  <
+                      decltype(std::declval<T&>()->to_sys(local_time<Duration>{},
+                                                          choose::earliest)),
+                      sys_time<duration>
+                  >::value
+              >::type>
+#endif
+        zoned_time(TimeZonePtr z, const local_time<Duration>& tp, choose c);
+
+    template <class Duration2, class TimeZonePtr2,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value
+                      >::type>
+        zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& zt);
+
+    template <class Duration2, class TimeZonePtr2,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value
+                      >::type>
+        zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& zt, choose);
+
+#if HAS_STRING_VIEW
+
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string_view())),
+                      sys_time<Duration>
+                  >::value
+              >::type>
+        zoned_time(std::string_view name, detail::nodeduct_t<const sys_time<Duration>&> st);
+
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string_view())),
+                      local_time<Duration>
+                  >::value
+              >::type>
+        zoned_time(std::string_view name, detail::nodeduct_t<const local_time<Duration>&> tp);
+
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string_view())),
+                      local_time<Duration>,
+                      choose
+                  >::value
+              >::type>
+        zoned_time(std::string_view name, detail::nodeduct_t<const local_time<Duration>&> tp, choose c);
+
+    template <class Duration2, class TimeZonePtr2, class T = TimeZonePtr,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value &&
+                          std::is_constructible
+                          <
+                              zoned_time,
+                              decltype(zoned_traits<T>::locate_zone(std::string_view())),
+                              zoned_time
+                          >::value
+                      >::type>
+        zoned_time(std::string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt);
+
+    template <class Duration2, class TimeZonePtr2, class T = TimeZonePtr,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value &&
+                          std::is_constructible
+                          <
+                              zoned_time,
+                              decltype(zoned_traits<T>::locate_zone(std::string_view())),
+                              zoned_time,
+                              choose
+                          >::value
+                      >::type>
+        zoned_time(std::string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt, choose);
+
+#else  // !HAS_STRING_VIEW
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string())),
+                      sys_time<Duration>
+                  >::value
+              >::type>
+#endif
+        zoned_time(const std::string& name, const sys_time<Duration>& st);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string())),
+                      sys_time<Duration>
+                  >::value
+              >::type>
+#endif
+        zoned_time(const char* name, const sys_time<Duration>& st);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string())),
+                      local_time<Duration>
+                  >::value
+              >::type>
+#endif
+        zoned_time(const std::string& name, const local_time<Duration>& tp);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string())),
+                      local_time<Duration>
+                  >::value
+              >::type>
+#endif
+        zoned_time(const char* name, const local_time<Duration>& tp);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string())),
+                      local_time<Duration>,
+                      choose
+                  >::value
+              >::type>
+#endif
+        zoned_time(const std::string& name, const local_time<Duration>& tp, choose c);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class T = TimeZonePtr,
+              class = typename std::enable_if
+              <
+                  std::is_constructible
+                  <
+                      zoned_time,
+                      decltype(zoned_traits<T>::locate_zone(std::string())),
+                      local_time<Duration>,
+                      choose
+                  >::value
+              >::type>
+#endif
+        zoned_time(const char* name, const local_time<Duration>& tp, choose c);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class Duration2, class TimeZonePtr2, class T = TimeZonePtr,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value &&
+                          std::is_constructible
+                          <
+                              zoned_time,
+                              decltype(zoned_traits<T>::locate_zone(std::string())),
+                              zoned_time
+                          >::value
+                      >::type>
+#else
+    template <class Duration2, class TimeZonePtr2>
+#endif
+        zoned_time(const std::string& name, const zoned_time<Duration2, TimeZonePtr2>& zt);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class Duration2, class TimeZonePtr2, class T = TimeZonePtr,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value &&
+                          std::is_constructible
+                          <
+                              zoned_time,
+                              decltype(zoned_traits<T>::locate_zone(std::string())),
+                              zoned_time
+                          >::value
+                      >::type>
+#else
+    template <class Duration2, class TimeZonePtr2>
+#endif
+        zoned_time(const char* name, const zoned_time<Duration2, TimeZonePtr2>& zt);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class Duration2, class TimeZonePtr2, class T = TimeZonePtr,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value &&
+                          std::is_constructible
+                          <
+                              zoned_time,
+                              decltype(zoned_traits<T>::locate_zone(std::string())),
+                              zoned_time,
+                              choose
+                          >::value
+                      >::type>
+#else
+    template <class Duration2, class TimeZonePtr2>
+#endif
+        zoned_time(const std::string& name, const zoned_time<Duration2, TimeZonePtr2>& zt,
+                   choose);
+
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+    template <class Duration2, class TimeZonePtr2, class T = TimeZonePtr,
+              class = typename std::enable_if
+                      <
+                          std::is_convertible<sys_time<Duration2>,
+                                              sys_time<Duration>>::value &&
+                          std::is_constructible
+                          <
+                              zoned_time,
+                              decltype(zoned_traits<T>::locate_zone(std::string())),
+                              zoned_time,
+                              choose
+                          >::value
+                      >::type>
+#else
+    template <class Duration2, class TimeZonePtr2>
+#endif
+        zoned_time(const char* name, const zoned_time<Duration2, TimeZonePtr2>& zt,
+                   choose);
+
+#endif  // !HAS_STRING_VIEW
+
+    zoned_time& operator=(const sys_time<Duration>& st);
+    zoned_time& operator=(const local_time<Duration>& ut);
+
+    explicit operator sys_time<duration>() const;
+    explicit operator local_time<duration>() const;
+
+    TimeZonePtr          get_time_zone() const;
+    local_time<duration> get_local_time() const;
+    sys_time<duration>   get_sys_time() const;
+    sys_info             get_info() const;
+
+    template <class Duration1, class Duration2, class TimeZonePtr1>
+    friend
+    bool
+    operator==(const zoned_time<Duration1, TimeZonePtr1>& x,
+               const zoned_time<Duration2, TimeZonePtr1>& y);
+
+    template <class CharT, class Traits, class Duration1, class TimeZonePtr1>
+    friend
+    std::basic_ostream<CharT, Traits>&
+    operator<<(std::basic_ostream<CharT, Traits>& os,
+               const zoned_time<Duration1, TimeZonePtr1>& t);
+
+private:
+    template <class D, class T> friend class zoned_time;
+};
+
+using zoned_seconds = zoned_time<std::chrono::seconds>;
+
+#if HAS_DEDUCTION_GUIDES
+
+namespace detail
+{
+   template<typename TimeZonePtrOrName>
+   using time_zone_representation =
+       std::conditional_t
+       <
+           std::is_convertible<TimeZonePtrOrName, std::string_view>::value,
+           time_zone const*,
+           std::remove_cv_t<std::remove_reference_t<TimeZonePtrOrName>>
+       >;
+}
+
+zoned_time()
+    -> zoned_time<std::chrono::seconds>;
+
+template <class Duration>
+zoned_time(sys_time<Duration>)
+    -> zoned_time<std::common_type_t<Duration, std::chrono::seconds>>;
+
+template <class TimeZonePtrOrName>
+zoned_time(TimeZonePtrOrName&&)
+    -> zoned_time<std::chrono::seconds, detail::time_zone_representation<TimeZonePtrOrName>>;
+
+template <class TimeZonePtrOrName, class Duration>
+zoned_time(TimeZonePtrOrName&&, sys_time<Duration>)
+    -> zoned_time<std::common_type_t<Duration, std::chrono::seconds>, detail::time_zone_representation<TimeZonePtrOrName>>;
+
+template <class TimeZonePtrOrName, class Duration>
+zoned_time(TimeZonePtrOrName&&, local_time<Duration>, choose = choose::earliest)
+    -> zoned_time<std::common_type_t<Duration, std::chrono::seconds>, detail::time_zone_representation<TimeZonePtrOrName>>;
+
+template <class Duration, class TimeZonePtrOrName, class TimeZonePtr2>
+zoned_time(TimeZonePtrOrName&&, zoned_time<Duration, TimeZonePtr2>, choose = choose::earliest)
+    -> zoned_time<std::common_type_t<Duration, std::chrono::seconds>, detail::time_zone_representation<TimeZonePtrOrName>>;
+
+#endif  // HAS_DEDUCTION_GUIDES
+
+template <class Duration1, class Duration2, class TimeZonePtr>
+inline
+bool
+operator==(const zoned_time<Duration1, TimeZonePtr>& x,
+           const zoned_time<Duration2, TimeZonePtr>& y)
+{
+    return x.zone_ == y.zone_ && x.tp_ == y.tp_;
+}
+
+template <class Duration1, class Duration2, class TimeZonePtr>
+inline
+bool
+operator!=(const zoned_time<Duration1, TimeZonePtr>& x,
+           const zoned_time<Duration2, TimeZonePtr>& y)
+{
+    return !(x == y);
+}
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+namespace detail
+{
+#  if USE_OS_TZDB
+    struct transition;
+    struct expanded_ttinfo;
+#  else  // !USE_OS_TZDB
+    struct zonelet;
+    class Rule;
+#  endif  // !USE_OS_TZDB
+}
+
+#endif  // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+class time_zone
+{
+private:
+    std::string                          name_;
+#if USE_OS_TZDB
+    std::vector<detail::transition>      transitions_;
+    std::vector<detail::expanded_ttinfo> ttinfos_;
+#else  // !USE_OS_TZDB
+    std::vector<detail::zonelet>         zonelets_;
+#endif  // !USE_OS_TZDB
+    std::unique_ptr<std::once_flag>      adjusted_;
+
+public:
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    time_zone(time_zone&&) = default;
+    time_zone& operator=(time_zone&&) = default;
+#else   // defined(_MSC_VER) && (_MSC_VER < 1900)
+    time_zone(time_zone&& src);
+    time_zone& operator=(time_zone&& src);
+#endif  // defined(_MSC_VER) && (_MSC_VER < 1900)
+
+    DATE_API explicit time_zone(const std::string& s, detail::undocumented);
+
+    const std::string& name() const NOEXCEPT;
+
+    template <class Duration> sys_info   get_info(sys_time<Duration> st) const;
+    template <class Duration> local_info get_info(local_time<Duration> tp) const;
+
+    template <class Duration>
+        sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys(local_time<Duration> tp) const;
+
+    template <class Duration>
+        sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys(local_time<Duration> tp, choose z) const;
+
+    template <class Duration>
+        local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_local(sys_time<Duration> tp) const;
+
+    friend bool operator==(const time_zone& x, const time_zone& y) NOEXCEPT;
+    friend bool operator< (const time_zone& x, const time_zone& y) NOEXCEPT;
+    friend DATE_API std::ostream& operator<<(std::ostream& os, const time_zone& z);
+
+#if !USE_OS_TZDB
+    DATE_API void add(const std::string& s);
+#endif  // !USE_OS_TZDB
+
+private:
+    DATE_API sys_info   get_info_impl(sys_seconds tp) const;
+    DATE_API local_info get_info_impl(local_seconds tp) const;
+
+    template <class Duration>
+        sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys_impl(local_time<Duration> tp, choose z, std::false_type) const;
+    template <class Duration>
+        sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+        to_sys_impl(local_time<Duration> tp, choose, std::true_type) const;
+
+#if USE_OS_TZDB
+    DATE_API void init() const;
+    DATE_API void init_impl();
+    DATE_API sys_info
+        load_sys_info(std::vector<detail::transition>::const_iterator i) const;
+
+    template <class TimeType>
+    DATE_API void
+    load_data(std::istream& inf, std::int32_t tzh_leapcnt, std::int32_t tzh_timecnt,
+                                 std::int32_t tzh_typecnt, std::int32_t tzh_charcnt);
+#else  // !USE_OS_TZDB
+    DATE_API sys_info   get_info_impl(sys_seconds tp, int timezone) const;
+    DATE_API void adjust_infos(const std::vector<detail::Rule>& rules);
+    DATE_API void parse_info(std::istream& in);
+#endif  // !USE_OS_TZDB
+};
+
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+
+inline
+time_zone::time_zone(time_zone&& src)
+    : name_(std::move(src.name_))
+    , zonelets_(std::move(src.zonelets_))
+    , adjusted_(std::move(src.adjusted_))
+    {}
+
+inline
+time_zone&
+time_zone::operator=(time_zone&& src)
+{
+    name_ = std::move(src.name_);
+    zonelets_ = std::move(src.zonelets_);
+    adjusted_ = std::move(src.adjusted_);
+    return *this;
+}
+
+#endif  // defined(_MSC_VER) && (_MSC_VER < 1900)
+
+inline
+const std::string&
+time_zone::name() const NOEXCEPT
+{
+    return name_;
+}
+
+template <class Duration>
+inline
+sys_info
+time_zone::get_info(sys_time<Duration> st) const
+{
+    return get_info_impl(date::floor<std::chrono::seconds>(st));
+}
+
+template <class Duration>
+inline
+local_info
+time_zone::get_info(local_time<Duration> tp) const
+{
+    return get_info_impl(date::floor<std::chrono::seconds>(tp));
+}
+
+template <class Duration>
+inline
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys(local_time<Duration> tp) const
+{
+    return to_sys_impl(tp, choose{}, std::true_type{});
+}
+
+template <class Duration>
+inline
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys(local_time<Duration> tp, choose z) const
+{
+    return to_sys_impl(tp, z, std::false_type{});
+}
+
+template <class Duration>
+inline
+local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_local(sys_time<Duration> tp) const
+{
+    using LT = local_time<typename std::common_type<Duration, std::chrono::seconds>::type>;
+    auto i = get_info(tp);
+    return LT{(tp + i.offset).time_since_epoch()};
+}
+
+inline bool operator==(const time_zone& x, const time_zone& y) NOEXCEPT {return x.name_ == y.name_;}
+inline bool operator< (const time_zone& x, const time_zone& y) NOEXCEPT {return x.name_ < y.name_;}
+
+inline bool operator!=(const time_zone& x, const time_zone& y) NOEXCEPT {return !(x == y);}
+inline bool operator> (const time_zone& x, const time_zone& y) NOEXCEPT {return   y < x;}
+inline bool operator<=(const time_zone& x, const time_zone& y) NOEXCEPT {return !(y < x);}
+inline bool operator>=(const time_zone& x, const time_zone& y) NOEXCEPT {return !(x < y);}
+
+template <class Duration>
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys_impl(local_time<Duration> tp, choose z, std::false_type) const
+{
+    auto i = get_info(tp);
+    if (i.result == local_info::nonexistent)
+    {
+        return i.first.end;
+    }
+    else if (i.result == local_info::ambiguous)
+    {
+        if (z == choose::latest)
+            return sys_time<Duration>{tp.time_since_epoch()} - i.second.offset;
+    }
+    return sys_time<Duration>{tp.time_since_epoch()} - i.first.offset;
+}
+
+template <class Duration>
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+time_zone::to_sys_impl(local_time<Duration> tp, choose, std::true_type) const
+{
+    auto i = get_info(tp);
+    if (i.result == local_info::nonexistent)
+        throw nonexistent_local_time(tp, i);
+    else if (i.result == local_info::ambiguous)
+        throw ambiguous_local_time(tp, i);
+    return sys_time<Duration>{tp.time_since_epoch()} - i.first.offset;
+}
+
+#if !USE_OS_TZDB
+
+class time_zone_link
+{
+private:
+    std::string name_;
+    std::string target_;
+public:
+    DATE_API explicit time_zone_link(const std::string& s);
+
+    const std::string& name() const {return name_;}
+    const std::string& target() const {return target_;}
+
+    friend bool operator==(const time_zone_link& x, const time_zone_link& y) {return x.name_ == y.name_;}
+    friend bool operator< (const time_zone_link& x, const time_zone_link& y) {return x.name_ < y.name_;}
+
+    friend DATE_API std::ostream& operator<<(std::ostream& os, const time_zone_link& x);
+};
+
+using link = time_zone_link;
+
+inline bool operator!=(const time_zone_link& x, const time_zone_link& y) {return !(x == y);}
+inline bool operator> (const time_zone_link& x, const time_zone_link& y) {return   y < x;}
+inline bool operator<=(const time_zone_link& x, const time_zone_link& y) {return !(y < x);}
+inline bool operator>=(const time_zone_link& x, const time_zone_link& y) {return !(x < y);}
+
+#endif  // !USE_OS_TZDB
+
+#if !MISSING_LEAP_SECONDS
+
+class leap_second
+{
+private:
+    sys_seconds date_;
+
+public:
+#if USE_OS_TZDB
+    DATE_API explicit leap_second(const sys_seconds& s, detail::undocumented);
+#else
+    DATE_API explicit leap_second(const std::string& s, detail::undocumented);
+#endif
+
+    sys_seconds date() const {return date_;}
+
+    friend bool operator==(const leap_second& x, const leap_second& y) {return x.date_ == y.date_;}
+    friend bool operator< (const leap_second& x, const leap_second& y) {return x.date_ < y.date_;}
+
+    template <class Duration>
+    friend
+    bool
+    operator==(const leap_second& x, const sys_time<Duration>& y)
+    {
+        return x.date_ == y;
+    }
+
+    template <class Duration>
+    friend
+    bool
+    operator< (const leap_second& x, const sys_time<Duration>& y)
+    {
+        return x.date_ < y;
+    }
+
+    template <class Duration>
+    friend
+    bool
+    operator< (const sys_time<Duration>& x, const leap_second& y)
+    {
+        return x < y.date_;
+    }
+
+    friend DATE_API std::ostream& operator<<(std::ostream& os, const leap_second& x);
+};
+
+inline bool operator!=(const leap_second& x, const leap_second& y) {return !(x == y);}
+inline bool operator> (const leap_second& x, const leap_second& y) {return   y < x;}
+inline bool operator<=(const leap_second& x, const leap_second& y) {return !(y < x);}
+inline bool operator>=(const leap_second& x, const leap_second& y) {return !(x < y);}
+
+template <class Duration>
+inline
+bool
+operator==(const sys_time<Duration>& x, const leap_second& y)
+{
+    return y == x;
+}
+
+template <class Duration>
+inline
+bool
+operator!=(const leap_second& x, const sys_time<Duration>& y)
+{
+    return !(x == y);
+}
+
+template <class Duration>
+inline
+bool
+operator!=(const sys_time<Duration>& x, const leap_second& y)
+{
+    return !(x == y);
+}
+
+template <class Duration>
+inline
+bool
+operator> (const leap_second& x, const sys_time<Duration>& y)
+{
+    return y < x;
+}
+
+template <class Duration>
+inline
+bool
+operator> (const sys_time<Duration>& x, const leap_second& y)
+{
+    return y < x;
+}
+
+template <class Duration>
+inline
+bool
+operator<=(const leap_second& x, const sys_time<Duration>& y)
+{
+    return !(y < x);
+}
+
+template <class Duration>
+inline
+bool
+operator<=(const sys_time<Duration>& x, const leap_second& y)
+{
+    return !(y < x);
+}
+
+template <class Duration>
+inline
+bool
+operator>=(const leap_second& x, const sys_time<Duration>& y)
+{
+    return !(x < y);
+}
+
+template <class Duration>
+inline
+bool
+operator>=(const sys_time<Duration>& x, const leap_second& y)
+{
+    return !(x < y);
+}
+
+using leap = leap_second;
+
+#endif  // !MISSING_LEAP_SECONDS
+
+#ifdef _WIN32
+
+namespace detail
+{
+
+// The time zone mapping is modelled after this data file:
+// http://unicode.org/repos/cldr/trunk/common/supplemental/windowsZones.xml
+// and the field names match the element names from the mapZone element
+// of windowsZones.xml.
+// The website displays this file here:
+// http://www.unicode.org/cldr/charts/latest/supplemental/zone_tzid.html
+// The html view is sorted before being displayed but is otherwise the same
+// There is a mapping between the os centric view (in this case windows)
+// the html displays uses and the generic view the xml file.
+// That mapping is this:
+// display column "windows" -> xml field "other".
+// display column "region"  -> xml field "territory".
+// display column "tzid"    -> xml field "type".
+// This structure uses the generic terminology because it could be
+// used to to support other os/native name conversions, not just windows,
+// and using the same generic names helps retain the connection to the
+// origin of the data that we are using.
+struct timezone_mapping
+{
+    timezone_mapping(const char* other, const char* territory, const char* type)
+        : other(other), territory(territory), type(type)
+    {
+    }
+    timezone_mapping() = default;
+    std::string other;
+    std::string territory;
+    std::string type;
+};
+
+}  // detail
+
+#endif  // _WIN32
+
+struct tzdb
+{
+    std::string                 version = "unknown";
+    std::vector<time_zone>      zones;
+#if !USE_OS_TZDB
+    std::vector<time_zone_link> links;
+#endif
+#if !MISSING_LEAP_SECONDS
+    std::vector<leap_second>    leap_seconds;
+#endif
+#if !USE_OS_TZDB
+    std::vector<detail::Rule>   rules;
+#endif
+#ifdef _WIN32
+    std::vector<detail::timezone_mapping> mappings;
+#endif
+    tzdb* next = nullptr;
+
+    tzdb() = default;
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    tzdb(tzdb&&) = default;
+    tzdb& operator=(tzdb&&) = default;
+#else  // defined(_MSC_VER) && (_MSC_VER < 1900)
+    tzdb(tzdb&& src)
+        : version(std::move(src.version))
+        , zones(std::move(src.zones))
+        , links(std::move(src.links))
+        , leap_seconds(std::move(src.leap_seconds))
+        , rules(std::move(src.rules))
+        , mappings(std::move(src.mappings))
+    {}
+
+    tzdb& operator=(tzdb&& src)
+    {
+        version = std::move(src.version);
+        zones = std::move(src.zones);
+        links = std::move(src.links);
+        leap_seconds = std::move(src.leap_seconds);
+        rules = std::move(src.rules);
+        mappings = std::move(src.mappings);
+        return *this;
+    }
+#endif  // defined(_MSC_VER) && (_MSC_VER < 1900)
+
+#if HAS_STRING_VIEW
+    const time_zone* locate_zone(std::string_view tz_name) const;
+#else
+    const time_zone* locate_zone(const std::string& tz_name) const;
+#endif
+    const time_zone* current_zone() const;
+};
+
+using TZ_DB = tzdb;
+
+DATE_API std::ostream&
+operator<<(std::ostream& os, const tzdb& db);
+
+DATE_API const tzdb& get_tzdb();
+
+class tzdb_list
+{
+    std::atomic<tzdb*> head_{nullptr};
+
+public:
+    ~tzdb_list();
+    tzdb_list() = default;
+    tzdb_list(tzdb_list&& x) noexcept;
+
+    const tzdb& front() const noexcept {return *head_;}
+          tzdb& front()       noexcept {return *head_;}
+
+    class const_iterator;
+
+    const_iterator begin() const noexcept;
+    const_iterator end() const noexcept;
+
+    const_iterator cbegin() const noexcept;
+    const_iterator cend() const noexcept;
+
+    const_iterator erase_after(const_iterator p) noexcept;
+
+    struct undocumented_helper;
+private:
+    void push_front(tzdb* tzdb) noexcept;
+};
+
+class tzdb_list::const_iterator
+{
+    tzdb* p_ = nullptr;
+
+    explicit const_iterator(tzdb* p) noexcept : p_{p} {}
+public:
+    const_iterator() = default;
+
+    using iterator_category = std::forward_iterator_tag;
+    using value_type        = tzdb;
+    using reference         = const value_type&;
+    using pointer           = const value_type*;
+    using difference_type   = std::ptrdiff_t;
+
+    reference operator*() const noexcept {return *p_;}
+    pointer  operator->() const noexcept {return p_;}
+
+    const_iterator& operator++() noexcept {p_ = p_->next; return *this;}
+    const_iterator  operator++(int) noexcept {auto t = *this; ++(*this); return t;}
+
+    friend
+    bool
+    operator==(const const_iterator& x, const const_iterator& y) noexcept
+        {return x.p_ == y.p_;}
+
+    friend
+    bool
+    operator!=(const const_iterator& x, const const_iterator& y) noexcept
+        {return !(x == y);}
+
+    friend class tzdb_list;
+};
+
+inline
+tzdb_list::const_iterator
+tzdb_list::begin() const noexcept
+{
+    return const_iterator{head_};
+}
+
+inline
+tzdb_list::const_iterator
+tzdb_list::end() const noexcept
+{
+    return const_iterator{nullptr};
+}
+
+inline
+tzdb_list::const_iterator
+tzdb_list::cbegin() const noexcept
+{
+    return begin();
+}
+
+inline
+tzdb_list::const_iterator
+tzdb_list::cend() const noexcept
+{
+    return end();
+}
+
+DATE_API tzdb_list& get_tzdb_list();
+
+#if !USE_OS_TZDB
+
+DATE_API const tzdb& reload_tzdb();
+DATE_API void        set_install(const std::string& install);
+
+#endif  // !USE_OS_TZDB
+
+#if HAS_REMOTE_API
+
+DATE_API std::string remote_version();
+// if provided error_buffer size should be at least CURL_ERROR_SIZE
+DATE_API bool        remote_download(const std::string& version, char* error_buffer = nullptr);
+DATE_API bool        remote_install(const std::string& version);
+
+#endif
+
+// zoned_time
+
+namespace detail
+{
+
+template <class T>
+inline
+T*
+to_raw_pointer(T* p) noexcept
+{
+    return p;
+}
+
+template <class Pointer>
+inline
+auto
+to_raw_pointer(Pointer p) noexcept
+    -> decltype(detail::to_raw_pointer(p.operator->()))
+{
+    return detail::to_raw_pointer(p.operator->());
+}
+
+}  // namespace detail
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time()
+    : zone_(zoned_traits<TimeZonePtr>::default_zone())
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const sys_time<Duration>& st)
+    : zone_(zoned_traits<TimeZonePtr>::default_zone())
+    , tp_(st)
+    {}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(TimeZonePtr z)
+    : zone_(std::move(z))
+    {assert(detail::to_raw_pointer(zone_) != nullptr);}
+
+#if HAS_STRING_VIEW
+
+template <class Duration, class TimeZonePtr>
+template <class T, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(std::string_view name)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name))
+    {}
+
+#else  // !HAS_STRING_VIEW
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const std::string& name)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name))
+    {}
+
+#endif  // !HAS_STRING_VIEW
+
+template <class Duration, class TimeZonePtr>
+template <class Duration2, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const zoned_time<Duration2, TimeZonePtr>& zt) NOEXCEPT
+    : zone_(zt.zone_)
+    , tp_(zt.tp_)
+    {}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(TimeZonePtr z, const sys_time<Duration>& st)
+    : zone_(std::move(z))
+    , tp_(st)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(TimeZonePtr z, const local_time<Duration>& t)
+    : zone_(std::move(z))
+    , tp_(zone_->to_sys(t))
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(TimeZonePtr z, const local_time<Duration>& t,
+                                              choose c)
+    : zone_(std::move(z))
+    , tp_(zone_->to_sys(t, c))
+    {}
+
+template <class Duration, class TimeZonePtr>
+template <class Duration2, class TimeZonePtr2, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(TimeZonePtr z,
+                                              const zoned_time<Duration2, TimeZonePtr2>& zt)
+    : zone_(std::move(z))
+    , tp_(zt.tp_)
+    {}
+
+template <class Duration, class TimeZonePtr>
+template <class Duration2, class TimeZonePtr2, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(TimeZonePtr z,
+                                      const zoned_time<Duration2, TimeZonePtr2>& zt, choose)
+    : zoned_time(std::move(z), zt)
+    {}
+
+#if HAS_STRING_VIEW
+
+template <class Duration, class TimeZonePtr>
+template <class T, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(std::string_view name,
+                                              detail::nodeduct_t<const sys_time<Duration>&> st)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), st)
+    {}
+
+template <class Duration, class TimeZonePtr>
+template <class T, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(std::string_view name,
+                                              detail::nodeduct_t<const local_time<Duration>&> t)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), t)
+    {}
+
+template <class Duration, class TimeZonePtr>
+template <class T, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(std::string_view name,
+                                              detail::nodeduct_t<const local_time<Duration>&> t, choose c)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), t, c)
+    {}
+
+template <class Duration, class TimeZonePtr>
+template <class Duration2, class TimeZonePtr2, class, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(std::string_view name,
+                                              const zoned_time<Duration2, TimeZonePtr2>& zt)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), zt)
+    {}
+
+template <class Duration, class TimeZonePtr>
+template <class Duration2, class TimeZonePtr2, class, class>
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(std::string_view name,
+                                              const zoned_time<Duration2, TimeZonePtr2>& zt,
+                                              choose c)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), zt, c)
+    {}
+
+#else  // !HAS_STRING_VIEW
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const std::string& name,
+                                              const sys_time<Duration>& st)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), st)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const char* name,
+                                              const sys_time<Duration>& st)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), st)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const std::string& name,
+                                              const local_time<Duration>& t)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), t)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const char* name,
+                                              const local_time<Duration>& t)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), t)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const std::string& name,
+                                              const local_time<Duration>& t, choose c)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), t, c)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class T, class>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const char* name,
+                                              const local_time<Duration>& t, choose c)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), t, c)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class Duration2, class TimeZonePtr2, class, class>
+#else
+template <class Duration2, class TimeZonePtr2>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const std::string& name,
+                                              const zoned_time<Duration2, TimeZonePtr2>& zt)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), zt)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class Duration2, class TimeZonePtr2, class, class>
+#else
+template <class Duration2, class TimeZonePtr2>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const char* name,
+                                              const zoned_time<Duration2, TimeZonePtr2>& zt)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), zt)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class Duration2, class TimeZonePtr2, class, class>
+#else
+template <class Duration2, class TimeZonePtr2>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const std::string& name,
+                                              const zoned_time<Duration2, TimeZonePtr2>& zt,
+                                              choose c)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), zt, c)
+    {}
+
+template <class Duration, class TimeZonePtr>
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+template <class Duration2, class TimeZonePtr2, class, class>
+#else
+template <class Duration2, class TimeZonePtr2>
+#endif
+inline
+zoned_time<Duration, TimeZonePtr>::zoned_time(const char* name,
+                                              const zoned_time<Duration2, TimeZonePtr2>& zt,
+                                              choose c)
+    : zoned_time(zoned_traits<TimeZonePtr>::locate_zone(name), zt, c)
+    {}
+
+#endif  // HAS_STRING_VIEW
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>&
+zoned_time<Duration, TimeZonePtr>::operator=(const sys_time<Duration>& st)
+{
+    tp_ = st;
+    return *this;
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>&
+zoned_time<Duration, TimeZonePtr>::operator=(const local_time<Duration>& ut)
+{
+    tp_ = zone_->to_sys(ut);
+    return *this;
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>::operator local_time<typename zoned_time<Duration, TimeZonePtr>::duration>() const
+{
+    return get_local_time();
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>::operator sys_time<typename zoned_time<Duration, TimeZonePtr>::duration>() const
+{
+    return get_sys_time();
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+TimeZonePtr
+zoned_time<Duration, TimeZonePtr>::get_time_zone() const
+{
+    return zone_;
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+local_time<typename zoned_time<Duration, TimeZonePtr>::duration>
+zoned_time<Duration, TimeZonePtr>::get_local_time() const
+{
+    return zone_->to_local(tp_);
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+sys_time<typename zoned_time<Duration, TimeZonePtr>::duration>
+zoned_time<Duration, TimeZonePtr>::get_sys_time() const
+{
+    return tp_;
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+sys_info
+zoned_time<Duration, TimeZonePtr>::get_info() const
+{
+    return zone_->get_info(tp_);
+}
+
+// make_zoned_time
+
+inline
+zoned_time<std::chrono::seconds>
+make_zoned()
+{
+    return zoned_time<std::chrono::seconds>();
+}
+
+template <class Duration>
+inline
+zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+make_zoned(const sys_time<Duration>& tp)
+{
+    return zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type>(tp);
+}
+
+template <class TimeZonePtr
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+#if !defined(__INTEL_COMPILER) || (__INTEL_COMPILER > 1600)
+          , class = typename std::enable_if
+          <
+            std::is_class
+            <
+                typename std::decay
+                <
+                    decltype(*detail::to_raw_pointer(std::declval<TimeZonePtr&>()))
+                >::type
+            >{}
+          >::type
+#endif
+#endif
+         >
+inline
+zoned_time<std::chrono::seconds, TimeZonePtr>
+make_zoned(TimeZonePtr z)
+{
+    return zoned_time<std::chrono::seconds, TimeZonePtr>(std::move(z));
+}
+
+inline
+zoned_seconds
+make_zoned(const std::string& name)
+{
+    return zoned_seconds(name);
+}
+
+template <class Duration, class TimeZonePtr
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+#if !defined(__INTEL_COMPILER) || (__INTEL_COMPILER > 1600)
+          , class = typename std::enable_if
+          <
+            std::is_class<typename std::decay<decltype(*std::declval<TimeZonePtr&>())>::type>{}
+          >::type
+#endif
+#endif
+         >
+inline
+zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type, TimeZonePtr>
+make_zoned(TimeZonePtr zone, const local_time<Duration>& tp)
+{
+    return zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type,
+                      TimeZonePtr>(std::move(zone), tp);
+}
+
+template <class Duration, class TimeZonePtr
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+#if !defined(__INTEL_COMPILER) || (__INTEL_COMPILER > 1600)
+          , class = typename std::enable_if
+          <
+            std::is_class<typename std::decay<decltype(*std::declval<TimeZonePtr&>())>::type>{}
+          >::type
+#endif
+#endif
+         >
+inline
+zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type, TimeZonePtr>
+make_zoned(TimeZonePtr zone, const local_time<Duration>& tp, choose c)
+{
+    return zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type,
+                      TimeZonePtr>(std::move(zone), tp, c);
+}
+
+template <class Duration>
+inline
+zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+make_zoned(const std::string& name, const local_time<Duration>& tp)
+{
+    return zoned_time<typename std::common_type<Duration,
+                      std::chrono::seconds>::type>(name, tp);
+}
+
+template <class Duration>
+inline
+zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+make_zoned(const std::string& name, const local_time<Duration>& tp, choose c)
+{
+    return zoned_time<typename std::common_type<Duration,
+                      std::chrono::seconds>::type>(name, tp, c);
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>
+make_zoned(TimeZonePtr zone, const zoned_time<Duration, TimeZonePtr>& zt)
+{
+    return zoned_time<Duration, TimeZonePtr>(std::move(zone), zt);
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>
+make_zoned(const std::string& name, const zoned_time<Duration, TimeZonePtr>& zt)
+{
+    return zoned_time<Duration, TimeZonePtr>(name, zt);
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>
+make_zoned(TimeZonePtr zone, const zoned_time<Duration, TimeZonePtr>& zt, choose c)
+{
+    return zoned_time<Duration, TimeZonePtr>(std::move(zone), zt, c);
+}
+
+template <class Duration, class TimeZonePtr>
+inline
+zoned_time<Duration, TimeZonePtr>
+make_zoned(const std::string& name, const zoned_time<Duration, TimeZonePtr>& zt, choose c)
+{
+    return zoned_time<Duration, TimeZonePtr>(name, zt, c);
+}
+
+template <class Duration, class TimeZonePtr
+#if !defined(_MSC_VER) || (_MSC_VER > 1916)
+#if !defined(__INTEL_COMPILER) || (__INTEL_COMPILER > 1600)
+          , class = typename std::enable_if
+          <
+            std::is_class<typename std::decay<decltype(*std::declval<TimeZonePtr&>())>::type>{}
+          >::type
+#endif
+#endif
+         >
+inline
+zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type, TimeZonePtr>
+make_zoned(TimeZonePtr zone, const sys_time<Duration>& st)
+{
+    return zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type,
+                      TimeZonePtr>(std::move(zone), st);
+}
+
+template <class Duration>
+inline
+zoned_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+make_zoned(const std::string& name, const sys_time<Duration>& st)
+{
+    return zoned_time<typename std::common_type<Duration,
+                      std::chrono::seconds>::type>(name, st);
+}
+
+template <class CharT, class Traits, class Duration, class TimeZonePtr>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const zoned_time<Duration, TimeZonePtr>& tp)
+{
+    using duration = typename zoned_time<Duration, TimeZonePtr>::duration;
+    using LT = local_time<duration>;
+    auto const st = tp.get_sys_time();
+    auto const info = tp.get_time_zone()->get_info(st);
+    return to_stream(os, fmt, LT{(st+info.offset).time_since_epoch()},
+                     &info.abbrev, &info.offset);
+}
+
+template <class CharT, class Traits, class Duration, class TimeZonePtr>
+inline
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const zoned_time<Duration, TimeZonePtr>& t)
+{
+    const CharT fmt[] = {'%', 'F', ' ', '%', 'T', ' ', '%', 'Z', CharT{}};
+    return to_stream(os, fmt, t);
+}
+
+#if !MISSING_LEAP_SECONDS
+
+class utc_clock
+{
+public:
+    using duration                  = std::chrono::system_clock::duration;
+    using rep                       = duration::rep;
+    using period                    = duration::period;
+    using time_point                = std::chrono::time_point<utc_clock>;
+    static CONSTDATA bool is_steady = false;
+
+    static time_point now();
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<std::chrono::system_clock, typename std::common_type<Duration, std::chrono::seconds>::type>
+    to_sys(const std::chrono::time_point<utc_clock, Duration>&);
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<utc_clock, typename std::common_type<Duration, std::chrono::seconds>::type>
+    from_sys(const std::chrono::time_point<std::chrono::system_clock, Duration>&);
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<local_t, typename std::common_type<Duration, std::chrono::seconds>::type>
+    to_local(const std::chrono::time_point<utc_clock, Duration>&);
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<utc_clock, typename std::common_type<Duration, std::chrono::seconds>::type>
+    from_local(const std::chrono::time_point<local_t, Duration>&);
+};
+
+template <class Duration>
+    using utc_time = std::chrono::time_point<utc_clock, Duration>;
+
+using utc_seconds = utc_time<std::chrono::seconds>;
+
+template <class Duration>
+utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+utc_clock::from_sys(const sys_time<Duration>& st)
+{
+    using std::chrono::seconds;
+    using CD = typename std::common_type<Duration, seconds>::type;
+    auto const& leaps = get_tzdb().leap_seconds;
+    auto const lt = std::upper_bound(leaps.begin(), leaps.end(), st);
+    return utc_time<CD>{st.time_since_epoch() + seconds{lt-leaps.begin()}};
+}
+
+// Return pair<is_leap_second, seconds{number_of_leap_seconds_since_1970}>
+// first is true if ut is during a leap second insertion, otherwise false.
+// If ut is during a leap second insertion, that leap second is included in the count
+template <class Duration>
+std::pair<bool, std::chrono::seconds>
+is_leap_second(date::utc_time<Duration> const& ut)
+{
+    using std::chrono::seconds;
+    using duration = typename std::common_type<Duration, seconds>::type;
+    auto const& leaps = get_tzdb().leap_seconds;
+    auto tp = sys_time<duration>{ut.time_since_epoch()};
+    auto const lt = std::upper_bound(leaps.begin(), leaps.end(), tp);
+    auto ds = seconds{lt-leaps.begin()};
+    tp -= ds;
+    auto ls = false;
+    if (lt > leaps.begin())
+    {
+        if (tp < lt[-1])
+        {
+            if (tp >= lt[-1].date() - seconds{1})
+                ls = true;
+            else
+                --ds;
+        }
+    }
+    return {ls, ds};
+}
+
+struct leap_second_info
+{
+    bool is_leap_second;
+    std::chrono::seconds elapsed;
+};
+
+template <class Duration>
+leap_second_info
+get_leap_second_info(date::utc_time<Duration> const& ut)
+{
+    auto p = is_leap_second(ut);
+    return {p.first, p.second};
+}
+
+template <class Duration>
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+utc_clock::to_sys(const utc_time<Duration>& ut)
+{
+    using std::chrono::seconds;
+    using CD = typename std::common_type<Duration, seconds>::type;
+    auto ls = is_leap_second(ut);
+    auto tp = sys_time<CD>{ut.time_since_epoch() - ls.second};
+    if (ls.first)
+        tp = floor<seconds>(tp) + seconds{1} - CD{1};
+    return tp;
+}
+
+inline
+utc_clock::time_point
+utc_clock::now()
+{
+    return from_sys(std::chrono::system_clock::now());
+}
+
+template <class Duration>
+utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+utc_clock::from_local(const local_time<Duration>& st)
+{
+    return from_sys(sys_time<Duration>{st.time_since_epoch()});
+}
+
+template <class Duration>
+local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+utc_clock::to_local(const utc_time<Duration>& ut)
+{
+    using CD = typename std::common_type<Duration, std::chrono::seconds>::type;
+    return local_time<CD>{to_sys(ut).time_since_epoch()};
+}
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const utc_time<Duration>& t)
+{
+    using std::chrono::seconds;
+    using CT = typename std::common_type<Duration, seconds>::type;
+    const std::string abbrev("UTC");
+    CONSTDATA seconds offset{0};
+    auto ls = is_leap_second(t);
+    auto tp = sys_time<CT>{t.time_since_epoch() - ls.second};
+    auto const sd = floor<days>(tp);
+    year_month_day ymd = sd;
+    auto time = make_time(tp - sys_seconds{sd});
+    time.seconds(detail::undocumented{}) += seconds{ls.first};
+    fields<CT> fds{ymd, time};
+    return to_stream(os, fmt, fds, &abbrev, &offset);
+}
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const utc_time<Duration>& t)
+{
+    const CharT fmt[] = {'%', 'F', ' ', '%', 'T', CharT{}};
+    return to_stream(os, fmt, t);
+}
+
+template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            utc_time<Duration>& tp, std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    using std::chrono::seconds;
+    using std::chrono::minutes;
+    using CT = typename std::common_type<Duration, seconds>::type;
+    minutes offset_local{};
+    auto offptr = offset ? offset : &offset_local;
+    fields<CT> fds{};
+    fds.has_tod = true;
+    from_stream(is, fmt, fds, abbrev, offptr);
+    if (!fds.ymd.ok())
+        is.setstate(std::ios::failbit);
+    if (!is.fail())
+    {
+        bool is_60_sec = fds.tod.seconds() == seconds{60};
+        if (is_60_sec)
+            fds.tod.seconds(detail::undocumented{}) -= seconds{1};
+        auto tmp = utc_clock::from_sys(sys_days(fds.ymd) - *offptr + fds.tod.to_duration());
+        if (is_60_sec)
+            tmp += seconds{1};
+        if (is_60_sec != is_leap_second(tmp).first || !fds.tod.in_conventional_range())
+        {
+            is.setstate(std::ios::failbit);
+            return is;
+        }
+        tp = std::chrono::time_point_cast<Duration>(tmp);
+    }
+    return is;
+}
+
+// tai_clock
+
+class tai_clock
+{
+public:
+    using duration                  = std::chrono::system_clock::duration;
+    using rep                       = duration::rep;
+    using period                    = duration::period;
+    using time_point                = std::chrono::time_point<tai_clock>;
+    static const bool is_steady     = false;
+
+    static time_point now();
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<utc_clock, typename std::common_type<Duration, std::chrono::seconds>::type>
+    to_utc(const std::chrono::time_point<tai_clock, Duration>&) NOEXCEPT;
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<tai_clock, typename std::common_type<Duration, std::chrono::seconds>::type>
+    from_utc(const std::chrono::time_point<utc_clock, Duration>&) NOEXCEPT;
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<local_t, typename std::common_type<Duration, date::days>::type>
+    to_local(const std::chrono::time_point<tai_clock, Duration>&) NOEXCEPT;
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<tai_clock, typename std::common_type<Duration, date::days>::type>
+    from_local(const std::chrono::time_point<local_t, Duration>&) NOEXCEPT;
+};
+
+template <class Duration>
+    using tai_time = std::chrono::time_point<tai_clock, Duration>;
+
+using tai_seconds = tai_time<std::chrono::seconds>;
+
+template <class Duration>
+inline
+utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+tai_clock::to_utc(const tai_time<Duration>& t) NOEXCEPT
+{
+    using std::chrono::seconds;
+    using CD = typename std::common_type<Duration, seconds>::type;
+    return utc_time<CD>{t.time_since_epoch()} -
+            (sys_days(year{1970}/January/1) - sys_days(year{1958}/January/1) + seconds{10});
+}
+
+template <class Duration>
+inline
+tai_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+tai_clock::from_utc(const utc_time<Duration>& t) NOEXCEPT
+{
+    using std::chrono::seconds;
+    using CD = typename std::common_type<Duration, seconds>::type;
+    return tai_time<CD>{t.time_since_epoch()} +
+            (sys_days(year{1970}/January/1) - sys_days(year{1958}/January/1) + seconds{10});
+}
+
+inline
+tai_clock::time_point
+tai_clock::now()
+{
+    return from_utc(utc_clock::now());
+}
+
+template <class Duration>
+inline
+local_time<typename std::common_type<Duration, date::days>::type>
+tai_clock::to_local(const tai_time<Duration>& t) NOEXCEPT
+{
+    using CD = typename std::common_type<Duration, date::days>::type;
+    return local_time<CD>{t.time_since_epoch()} -
+           (local_days(year{1970}/January/1) - local_days(year{1958}/January/1));
+}
+
+template <class Duration>
+inline
+tai_time<typename std::common_type<Duration, date::days>::type>
+tai_clock::from_local(const local_time<Duration>& t) NOEXCEPT
+{
+    using CD = typename std::common_type<Duration, date::days>::type;
+    return tai_time<CD>{t.time_since_epoch()} +
+            (local_days(year{1970}/January/1) - local_days(year{1958}/January/1));
+}
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const tai_time<Duration>& t)
+{
+    const std::string abbrev("TAI");
+    CONSTDATA std::chrono::seconds offset{0};
+    return to_stream(os, fmt, tai_clock::to_local(t), &abbrev, &offset);
+}
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const tai_time<Duration>& t)
+{
+    const CharT fmt[] = {'%', 'F', ' ', '%', 'T', CharT{}};
+    return to_stream(os, fmt, t);
+}
+
+template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            tai_time<Duration>& tp,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    local_time<Duration> lp;
+    from_stream(is, fmt, lp, abbrev, offset);
+    if (!is.fail())
+        tp = tai_clock::from_local(lp);
+    return is;
+}
+
+// gps_clock
+
+class gps_clock
+{
+public:
+    using duration                  = std::chrono::system_clock::duration;
+    using rep                       = duration::rep;
+    using period                    = duration::period;
+    using time_point                = std::chrono::time_point<gps_clock>;
+    static const bool is_steady     = false;
+
+    static time_point now();
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<utc_clock, typename std::common_type<Duration, std::chrono::seconds>::type>
+    to_utc(const std::chrono::time_point<gps_clock, Duration>&) NOEXCEPT;
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<gps_clock, typename std::common_type<Duration, std::chrono::seconds>::type>
+    from_utc(const std::chrono::time_point<utc_clock, Duration>&) NOEXCEPT;
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<local_t, typename std::common_type<Duration, date::days>::type>
+    to_local(const std::chrono::time_point<gps_clock, Duration>&) NOEXCEPT;
+
+    template<typename Duration>
+    static
+    std::chrono::time_point<gps_clock, typename std::common_type<Duration, date::days>::type>
+    from_local(const std::chrono::time_point<local_t, Duration>&) NOEXCEPT;
+};
+
+template <class Duration>
+    using gps_time = std::chrono::time_point<gps_clock, Duration>;
+
+using gps_seconds = gps_time<std::chrono::seconds>;
+
+template <class Duration>
+inline
+utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+gps_clock::to_utc(const gps_time<Duration>& t) NOEXCEPT
+{
+    using std::chrono::seconds;
+    using CD = typename std::common_type<Duration, seconds>::type;
+    return utc_time<CD>{t.time_since_epoch()} +
+            (sys_days(year{1980}/January/Sunday[1]) - sys_days(year{1970}/January/1) +
+             seconds{9});
+}
+
+template <class Duration>
+inline
+gps_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+gps_clock::from_utc(const utc_time<Duration>& t) NOEXCEPT
+{
+    using std::chrono::seconds;
+    using CD = typename std::common_type<Duration, seconds>::type;
+    return gps_time<CD>{t.time_since_epoch()} -
+            (sys_days(year{1980}/January/Sunday[1]) - sys_days(year{1970}/January/1) +
+             seconds{9});
+}
+
+inline
+gps_clock::time_point
+gps_clock::now()
+{
+    return from_utc(utc_clock::now());
+}
+
+template <class Duration>
+inline
+local_time<typename std::common_type<Duration, date::days>::type>
+gps_clock::to_local(const gps_time<Duration>& t) NOEXCEPT
+{
+    using CD = typename std::common_type<Duration, date::days>::type;
+    return local_time<CD>{t.time_since_epoch()} +
+            (local_days(year{1980}/January/Sunday[1]) - local_days(year{1970}/January/1));
+}
+
+template <class Duration>
+inline
+gps_time<typename std::common_type<Duration, date::days>::type>
+gps_clock::from_local(const local_time<Duration>& t) NOEXCEPT
+{
+    using CD = typename std::common_type<Duration, date::days>::type;
+    return gps_time<CD>{t.time_since_epoch()} -
+            (local_days(year{1980}/January/Sunday[1]) - local_days(year{1970}/January/1));
+}
+
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
+          const gps_time<Duration>& t)
+{
+    const std::string abbrev("GPS");
+    CONSTDATA std::chrono::seconds offset{0};
+    return to_stream(os, fmt, gps_clock::to_local(t), &abbrev, &offset);
+}
+
+template <class CharT, class Traits, class Duration>
+std::basic_ostream<CharT, Traits>&
+operator<<(std::basic_ostream<CharT, Traits>& os, const gps_time<Duration>& t)
+{
+    const CharT fmt[] = {'%', 'F', ' ', '%', 'T', CharT{}};
+    return to_stream(os, fmt, t);
+}
+
+template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
+std::basic_istream<CharT, Traits>&
+from_stream(std::basic_istream<CharT, Traits>& is, const CharT* fmt,
+            gps_time<Duration>& tp,
+            std::basic_string<CharT, Traits, Alloc>* abbrev = nullptr,
+            std::chrono::minutes* offset = nullptr)
+{
+    local_time<Duration> lp;
+    from_stream(is, fmt, lp, abbrev, offset);
+    if (!is.fail())
+        tp = gps_clock::from_local(lp);
+    return is;
+}
+
+// clock_time_conversion
+
+template <class DstClock, class SrcClock>
+struct clock_time_conversion
+{};
+
+template <>
+struct clock_time_conversion<std::chrono::system_clock, std::chrono::system_clock>
+{
+    template <class Duration>
+    sys_time<Duration>
+    operator()(const sys_time<Duration>& st) const
+    {
+        return st;
+    }
+};
+
+template <>
+struct clock_time_conversion<utc_clock, utc_clock>
+{
+    template <class Duration>
+    utc_time<Duration>
+    operator()(const utc_time<Duration>& ut) const
+    {
+        return ut;
+    }
+};
+
+template<>
+struct clock_time_conversion<local_t, local_t>
+{
+    template <class Duration>
+    local_time<Duration>
+    operator()(const local_time<Duration>& lt) const
+    {
+        return lt;
+    }
+};
+
+template <>
+struct clock_time_conversion<utc_clock, std::chrono::system_clock>
+{
+    template <class Duration>
+    utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+    operator()(const sys_time<Duration>& st) const
+    {
+        return utc_clock::from_sys(st);
+    }
+};
+
+template <>
+struct clock_time_conversion<std::chrono::system_clock, utc_clock>
+{
+    template <class Duration>
+    sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+    operator()(const utc_time<Duration>& ut) const
+    {
+        return utc_clock::to_sys(ut);
+    }
+};
+
+template<>
+struct clock_time_conversion<local_t, std::chrono::system_clock>
+{
+    template <class Duration>
+    local_time<Duration>
+    operator()(const sys_time<Duration>& st) const
+    {
+       return local_time<Duration>{st.time_since_epoch()};
+    }
+};
+
+template<>
+struct clock_time_conversion<std::chrono::system_clock, local_t>
+{
+    template <class Duration>
+    sys_time<Duration>
+    operator()(const local_time<Duration>& lt) const
+    {
+        return sys_time<Duration>{lt.time_since_epoch()};
+    }
+};
+
+template<>
+struct clock_time_conversion<utc_clock, local_t>
+{
+    template <class Duration>
+    utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+    operator()(const local_time<Duration>& lt) const
+    {
+       return utc_clock::from_local(lt);
+    }
+};
+
+template<>
+struct clock_time_conversion<local_t, utc_clock>
+{
+    template <class Duration>
+    local_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+    operator()(const utc_time<Duration>& ut) const
+    {
+       return utc_clock::to_local(ut);
+    }
+};
+
+template<typename Clock>
+struct clock_time_conversion<Clock, Clock>
+{
+    template <class Duration>
+    std::chrono::time_point<Clock, Duration>
+    operator()(const std::chrono::time_point<Clock, Duration>& tp) const
+    {
+        return tp;
+    }
+};
+
+namespace ctc_detail
+{
+
+template <class Clock, class Duration>
+    using time_point = std::chrono::time_point<Clock, Duration>;
+
+using std::declval;
+using std::chrono::system_clock;
+
+//Check if TimePoint is time for given clock,
+//if not emits hard error
+template <class Clock, class TimePoint>
+struct return_clock_time
+{
+    using clock_time_point = time_point<Clock, typename TimePoint::duration>;
+    using type             = TimePoint;
+
+    static_assert(std::is_same<TimePoint, clock_time_point>::value,
+                  "time point with appropariate clock shall be returned");
+};
+
+// Check if Clock has to_sys method accepting TimePoint with given duration const& and
+// returning sys_time. If so has nested type member equal to return type to_sys.
+template <class Clock, class Duration, class = void>
+struct return_to_sys
+{};
+
+template <class Clock, class Duration>
+struct return_to_sys
+       <
+           Clock, Duration,
+           decltype(Clock::to_sys(declval<time_point<Clock, Duration> const&>()), void())
+       >
+    : return_clock_time
+      <
+          system_clock,
+          decltype(Clock::to_sys(declval<time_point<Clock, Duration> const&>()))
+      >
+{};
+
+// Similiar to above
+template <class Clock, class Duration, class = void>
+struct return_from_sys
+{};
+
+template <class Clock, class Duration>
+struct return_from_sys
+       <
+           Clock, Duration,
+           decltype(Clock::from_sys(declval<time_point<system_clock, Duration> const&>()),
+                    void())
+       >
+    : return_clock_time
+      <
+          Clock,
+          decltype(Clock::from_sys(declval<time_point<system_clock, Duration> const&>()))
+      >
+{};
+
+// Similiar to above
+template <class Clock, class Duration, class = void>
+struct return_to_utc
+{};
+
+template <class Clock, class Duration>
+struct return_to_utc
+       <
+           Clock, Duration,
+           decltype(Clock::to_utc(declval<time_point<Clock, Duration> const&>()), void())
+       >
+    : return_clock_time
+      <
+          utc_clock,
+          decltype(Clock::to_utc(declval<time_point<Clock, Duration> const&>()))>
+{};
+
+// Similiar to above
+template <class Clock, class Duration, class = void>
+struct return_from_utc
+{};
+
+template <class Clock, class Duration>
+struct return_from_utc
+       <
+           Clock, Duration,
+           decltype(Clock::from_utc(declval<time_point<utc_clock, Duration> const&>()),
+                    void())
+       >
+    : return_clock_time
+      <
+          Clock,
+          decltype(Clock::from_utc(declval<time_point<utc_clock, Duration> const&>()))
+      >
+{};
+
+// Similiar to above
+template<typename Clock, typename Duration, typename = void>
+struct return_to_local
+{};
+
+template<typename Clock, typename Duration>
+struct return_to_local
+       <
+          Clock, Duration,
+          decltype(Clock::to_local(declval<time_point<Clock, Duration> const&>()),
+                   void())
+       >
+     : return_clock_time
+       <
+           local_t,
+           decltype(Clock::to_local(declval<time_point<Clock, Duration> const&>()))
+       >
+{};
+
+// Similiar to above
+template<typename Clock, typename Duration, typename = void>
+struct return_from_local
+{};
+
+template<typename Clock, typename Duration>
+struct return_from_local
+       <
+           Clock, Duration,
+           decltype(Clock::from_local(declval<time_point<local_t, Duration> const&>()),
+                    void())
+       >
+     : return_clock_time
+       <
+           Clock,
+           decltype(Clock::from_local(declval<time_point<local_t, Duration> const&>()))
+       >
+{};
+
+}  // namespace ctc_detail
+
+template <class SrcClock>
+struct clock_time_conversion<std::chrono::system_clock, SrcClock>
+{
+    template <class Duration>
+    typename ctc_detail::return_to_sys<SrcClock, Duration>::type
+    operator()(const std::chrono::time_point<SrcClock, Duration>& tp) const
+    {
+        return SrcClock::to_sys(tp);
+    }
+};
+
+template <class DstClock>
+struct clock_time_conversion<DstClock, std::chrono::system_clock>
+{
+    template <class Duration>
+    typename ctc_detail::return_from_sys<DstClock, Duration>::type
+    operator()(const sys_time<Duration>& st) const
+    {
+        return DstClock::from_sys(st);
+    }
+};
+
+template <class SrcClock>
+struct clock_time_conversion<utc_clock, SrcClock>
+{
+    template <class Duration>
+    typename ctc_detail::return_to_utc<SrcClock, Duration>::type
+    operator()(const std::chrono::time_point<SrcClock, Duration>& tp) const
+    {
+        return SrcClock::to_utc(tp);
+    }
+};
+
+template <class DstClock>
+struct clock_time_conversion<DstClock, utc_clock>
+{
+    template <class Duration>
+    typename ctc_detail::return_from_utc<DstClock, Duration>::type
+    operator()(const utc_time<Duration>& ut) const
+    {
+        return DstClock::from_utc(ut);
+    }
+};
+
+template<typename SrcClock>
+struct clock_time_conversion<local_t, SrcClock>
+{
+    template <class Duration>
+    typename ctc_detail::return_to_local<SrcClock, Duration>::type
+    operator()(const std::chrono::time_point<SrcClock, Duration>& tp) const
+    {
+        return SrcClock::to_local(tp);
+    }
+};
+
+template<typename DstClock>
+struct clock_time_conversion<DstClock, local_t>
+{
+    template <class Duration>
+    typename ctc_detail::return_from_local<DstClock, Duration>::type
+    operator()(const local_time<Duration>& lt) const
+    {
+        return DstClock::from_local(lt);
+    }
+};
+
+namespace clock_cast_detail
+{
+
+template <class Clock, class Duration>
+    using time_point = std::chrono::time_point<Clock, Duration>;
+using std::chrono::system_clock;
+
+template <class DstClock, class SrcClock, class Duration>
+auto
+conv_clock(const time_point<SrcClock, Duration>& t)
+    -> decltype(std::declval<clock_time_conversion<DstClock, SrcClock>>()(t))
+{
+    return clock_time_conversion<DstClock, SrcClock>{}(t);
+}
+
+//direct trait conversion, 1st candidate
+template <class DstClock, class SrcClock, class Duration>
+auto
+cc_impl(const time_point<SrcClock, Duration>& t, const time_point<SrcClock, Duration>*)
+    -> decltype(conv_clock<DstClock>(t))
+{
+    return conv_clock<DstClock>(t);
+}
+
+//conversion through sys, 2nd candidate
+template <class DstClock, class SrcClock, class Duration>
+auto
+cc_impl(const time_point<SrcClock, Duration>& t, const void*)
+    -> decltype(conv_clock<DstClock>(conv_clock<system_clock>(t)))
+{
+    return conv_clock<DstClock>(conv_clock<system_clock>(t));
+}
+
+//conversion through utc, 2nd candidate
+template <class DstClock, class SrcClock, class Duration>
+auto
+cc_impl(const time_point<SrcClock, Duration>& t, const void*)
+    -> decltype(0,  // MSVC_WORKAROUND
+                conv_clock<DstClock>(conv_clock<utc_clock>(t)))
+{
+    return conv_clock<DstClock>(conv_clock<utc_clock>(t));
+}
+
+//conversion through sys and utc, 3rd candidate
+template <class DstClock, class SrcClock, class Duration>
+auto
+cc_impl(const time_point<SrcClock, Duration>& t, ...)
+    -> decltype(conv_clock<DstClock>(conv_clock<utc_clock>(conv_clock<system_clock>(t))))
+{
+    return conv_clock<DstClock>(conv_clock<utc_clock>(conv_clock<system_clock>(t)));
+}
+
+//conversion through utc and sys, 3rd candidate
+template <class DstClock, class SrcClock, class Duration>
+auto
+cc_impl(const time_point<SrcClock, Duration>& t, ...)
+    -> decltype(0,  // MSVC_WORKAROUND
+                conv_clock<DstClock>(conv_clock<system_clock>(conv_clock<utc_clock>(t))))
+{
+    return conv_clock<DstClock>(conv_clock<system_clock>(conv_clock<utc_clock>(t)));
+}
+
+}  // namespace clock_cast_detail
+
+template <class DstClock, class SrcClock, class Duration>
+auto
+clock_cast(const std::chrono::time_point<SrcClock, Duration>& tp)
+    -> decltype(clock_cast_detail::cc_impl<DstClock>(tp, &tp))
+{
+    return clock_cast_detail::cc_impl<DstClock>(tp, &tp);
+}
+
+// Deprecated API
+
+template <class Duration>
+inline
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_sys_time(const utc_time<Duration>& t)
+{
+    return utc_clock::to_sys(t);
+}
+
+template <class Duration>
+inline
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_sys_time(const tai_time<Duration>& t)
+{
+    return utc_clock::to_sys(tai_clock::to_utc(t));
+}
+
+template <class Duration>
+inline
+sys_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_sys_time(const gps_time<Duration>& t)
+{
+    return utc_clock::to_sys(gps_clock::to_utc(t));
+}
+
+
+template <class Duration>
+inline
+utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_utc_time(const sys_time<Duration>& t)
+{
+    return utc_clock::from_sys(t);
+}
+
+template <class Duration>
+inline
+utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_utc_time(const tai_time<Duration>& t)
+{
+    return tai_clock::to_utc(t);
+}
+
+template <class Duration>
+inline
+utc_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_utc_time(const gps_time<Duration>& t)
+{
+    return gps_clock::to_utc(t);
+}
+
+
+template <class Duration>
+inline
+tai_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_tai_time(const sys_time<Duration>& t)
+{
+    return tai_clock::from_utc(utc_clock::from_sys(t));
+}
+
+template <class Duration>
+inline
+tai_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_tai_time(const utc_time<Duration>& t)
+{
+    return tai_clock::from_utc(t);
+}
+
+template <class Duration>
+inline
+tai_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_tai_time(const gps_time<Duration>& t)
+{
+    return tai_clock::from_utc(gps_clock::to_utc(t));
+}
+
+
+template <class Duration>
+inline
+gps_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_gps_time(const sys_time<Duration>& t)
+{
+    return gps_clock::from_utc(utc_clock::from_sys(t));
+}
+
+template <class Duration>
+inline
+gps_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_gps_time(const utc_time<Duration>& t)
+{
+    return gps_clock::from_utc(t);
+}
+
+template <class Duration>
+inline
+gps_time<typename std::common_type<Duration, std::chrono::seconds>::type>
+to_gps_time(const tai_time<Duration>& t)
+{
+    return gps_clock::from_utc(tai_clock::to_utc(t));
+}
+
+#endif  // !MISSING_LEAP_SECONDS
+
+}  // namespace date
+
+#endif  // TZ_H
diff --git a/src/libs/date/includes/date/tz_private.h b/src/libs/date/includes/date/tz_private.h
new file mode 100644
index 00000000..798fcf5a
--- /dev/null
+++ b/src/libs/date/includes/date/tz_private.h
@@ -0,0 +1,316 @@
+#ifndef TZ_PRIVATE_H
+#define TZ_PRIVATE_H
+
+// The MIT License (MIT)
+//
+// Copyright (c) 2015, 2016 Howard Hinnant
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+#include "tz.h"
+#else
+#include "date.h"
+#include <vector>
+#endif
+
+namespace date
+{
+
+namespace detail
+{
+
+#if !USE_OS_TZDB
+
+enum class tz {utc, local, standard};
+
+//forward declare to avoid warnings in gcc 6.2
+class MonthDayTime;
+std::istream& operator>>(std::istream& is, MonthDayTime& x);
+std::ostream& operator<<(std::ostream& os, const MonthDayTime& x);
+
+
+class MonthDayTime
+{
+private:
+    struct pair
+    {
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+        pair() : month_day_(date::jan / 1), weekday_(0U) {}
+
+        pair(const date::month_day& month_day, const date::weekday& weekday)
+            : month_day_(month_day), weekday_(weekday) {}
+#endif
+
+        date::month_day month_day_;
+        date::weekday   weekday_;
+    };
+
+    enum Type {month_day, month_last_dow, lteq, gteq};
+
+    Type                         type_{month_day};
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    union U
+#else
+    struct U
+#endif
+    {
+        date::month_day          month_day_;
+        date::month_weekday_last month_weekday_last_;
+        pair                     month_day_weekday_;
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+        U() : month_day_{date::jan/1} {}
+#else
+        U() :
+            month_day_(date::jan/1),
+            month_weekday_last_(date::month(0U), date::weekday_last(date::weekday(0U)))
+        {}
+
+#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)
+
+        U& operator=(const date::month_day& x);
+        U& operator=(const date::month_weekday_last& x);
+        U& operator=(const pair& x);
+    } u;
+
+    std::chrono::hours           h_{};
+    std::chrono::minutes         m_{};
+    std::chrono::seconds         s_{};
+    tz                           zone_{tz::local};
+
+public:
+    MonthDayTime() = default;
+    MonthDayTime(local_seconds tp, tz timezone);
+    MonthDayTime(const date::month_day& md, tz timezone);
+
+    date::day day() const;
+    date::month month() const;
+    tz zone() const {return zone_;}
+
+    void canonicalize(date::year y);
+
+    sys_seconds
+       to_sys(date::year y, std::chrono::seconds offset, std::chrono::seconds save) const;
+    sys_days to_sys_days(date::year y) const;
+
+    sys_seconds to_time_point(date::year y) const;
+    int compare(date::year y, const MonthDayTime& x, date::year yx,
+                std::chrono::seconds offset, std::chrono::minutes prev_save) const;
+
+    friend std::istream& operator>>(std::istream& is, MonthDayTime& x);
+    friend std::ostream& operator<<(std::ostream& os, const MonthDayTime& x);
+};
+
+// A Rule specifies one or more set of datetimes without using an offset.
+// Multiple dates are specified with multiple years.  The years in effect
+// go from starting_year_ to ending_year_, inclusive.  starting_year_ <=
+// ending_year_. save_ is in effect for times from the specified time
+// onward, including the specified time. When the specified time is
+// local, it uses the save_ from the chronologically previous Rule, or if
+// there is none, 0.
+
+//forward declare to avoid warnings in gcc 6.2
+class Rule;
+bool operator==(const Rule& x, const Rule& y);
+bool operator<(const Rule& x, const Rule& y);
+bool operator==(const Rule& x, const date::year& y);
+bool operator<(const Rule& x, const date::year& y);
+bool operator==(const date::year& x, const Rule& y);
+bool operator<(const date::year& x, const Rule& y);
+bool operator==(const Rule& x, const std::string& y);
+bool operator<(const Rule& x, const std::string& y);
+bool operator==(const std::string& x, const Rule& y);
+bool operator<(const std::string& x, const Rule& y);
+std::ostream& operator<<(std::ostream& os, const Rule& r);
+
+class Rule
+{
+private:
+    std::string          name_;
+    date::year           starting_year_{0};
+    date::year           ending_year_{0};
+    MonthDayTime         starting_at_;
+    std::chrono::minutes save_{0};
+    std::string          abbrev_;
+
+public:
+    Rule() = default;
+    explicit Rule(const std::string& s);
+    Rule(const Rule& r, date::year starting_year, date::year ending_year);
+
+    const std::string& name() const {return name_;}
+    const std::string& abbrev() const {return abbrev_;}
+
+    const MonthDayTime&         mdt()           const {return starting_at_;}
+    const date::year&           starting_year() const {return starting_year_;}
+    const date::year&           ending_year()   const {return ending_year_;}
+    const std::chrono::minutes& save()          const {return save_;}
+
+    static void split_overlaps(std::vector<Rule>& rules);
+
+    friend bool operator==(const Rule& x, const Rule& y);
+    friend bool operator<(const Rule& x, const Rule& y);
+    friend bool operator==(const Rule& x, const date::year& y);
+    friend bool operator<(const Rule& x, const date::year& y);
+    friend bool operator==(const date::year& x, const Rule& y);
+    friend bool operator<(const date::year& x, const Rule& y);
+    friend bool operator==(const Rule& x, const std::string& y);
+    friend bool operator<(const Rule& x, const std::string& y);
+    friend bool operator==(const std::string& x, const Rule& y);
+    friend bool operator<(const std::string& x, const Rule& y);
+
+    friend std::ostream& operator<<(std::ostream& os, const Rule& r);
+
+private:
+    date::day day() const;
+    date::month month() const;
+    static void split_overlaps(std::vector<Rule>& rules, std::size_t i, std::size_t& e);
+    static bool overlaps(const Rule& x, const Rule& y);
+    static void split(std::vector<Rule>& rules, std::size_t i, std::size_t k,
+                      std::size_t& e);
+};
+
+inline bool operator!=(const Rule& x, const Rule& y) {return !(x == y);}
+inline bool operator> (const Rule& x, const Rule& y) {return   y < x;}
+inline bool operator<=(const Rule& x, const Rule& y) {return !(y < x);}
+inline bool operator>=(const Rule& x, const Rule& y) {return !(x < y);}
+
+inline bool operator!=(const Rule& x, const date::year& y) {return !(x == y);}
+inline bool operator> (const Rule& x, const date::year& y) {return   y < x;}
+inline bool operator<=(const Rule& x, const date::year& y) {return !(y < x);}
+inline bool operator>=(const Rule& x, const date::year& y) {return !(x < y);}
+
+inline bool operator!=(const date::year& x, const Rule& y) {return !(x == y);}
+inline bool operator> (const date::year& x, const Rule& y) {return   y < x;}
+inline bool operator<=(const date::year& x, const Rule& y) {return !(y < x);}
+inline bool operator>=(const date::year& x, const Rule& y) {return !(x < y);}
+
+inline bool operator!=(const Rule& x, const std::string& y) {return !(x == y);}
+inline bool operator> (const Rule& x, const std::string& y) {return   y < x;}
+inline bool operator<=(const Rule& x, const std::string& y) {return !(y < x);}
+inline bool operator>=(const Rule& x, const std::string& y) {return !(x < y);}
+
+inline bool operator!=(const std::string& x, const Rule& y) {return !(x == y);}
+inline bool operator> (const std::string& x, const Rule& y) {return   y < x;}
+inline bool operator<=(const std::string& x, const Rule& y) {return !(y < x);}
+inline bool operator>=(const std::string& x, const Rule& y) {return !(x < y);}
+
+struct zonelet
+{
+    enum tag {has_rule, has_save, is_empty};
+
+    std::chrono::seconds gmtoff_;
+    tag tag_ = has_rule;
+
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    union U
+#else
+    struct U
+#endif
+    {
+        std::string          rule_;
+        std::chrono::minutes save_;
+
+        ~U() {}
+        U() {}
+        U(const U&) {}
+        U& operator=(const U&) = delete;
+    } u;
+
+    std::string                        format_;
+    date::year                         until_year_{0};
+    MonthDayTime                       until_date_;
+    sys_seconds                        until_utc_;
+    local_seconds                      until_std_;
+    local_seconds                      until_loc_;
+    std::chrono::minutes               initial_save_{};
+    std::string                        initial_abbrev_;
+    std::pair<const Rule*, date::year> first_rule_{nullptr, date::year::min()};
+    std::pair<const Rule*, date::year> last_rule_{nullptr, date::year::max()};
+
+    ~zonelet();
+    zonelet();
+    zonelet(const zonelet& i);
+    zonelet& operator=(const zonelet&) = delete;
+};
+
+#else  // USE_OS_TZDB
+
+struct ttinfo
+{
+    std::int32_t  tt_gmtoff;
+    unsigned char tt_isdst;
+    unsigned char tt_abbrind;
+    unsigned char pad[2];
+};
+
+static_assert(sizeof(ttinfo) == 8, "");
+
+struct expanded_ttinfo
+{
+    std::chrono::seconds offset;
+    std::string          abbrev;
+    bool                 is_dst;
+};
+
+struct transition
+{
+    sys_seconds            timepoint;
+    const expanded_ttinfo* info;
+
+    transition(sys_seconds tp, const expanded_ttinfo* i = nullptr)
+        : timepoint(tp)
+        , info(i)
+        {}
+
+    friend
+    std::ostream&
+    operator<<(std::ostream& os, const transition& t)
+    {
+        using date::operator<<;
+        os << t.timepoint << "Z ";
+        if (t.info->offset >= std::chrono::seconds{0})
+            os << '+';
+        os << make_time(t.info->offset);
+        if (t.info->is_dst > 0)
+            os << " daylight ";
+        else
+            os << " standard ";
+        os << t.info->abbrev;
+        return os;
+    }
+};
+
+#endif  // USE_OS_TZDB
+
+}  // namespace detail
+
+}  // namespace date
+
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#include "tz.h"
+#endif
+
+#endif  // TZ_PRIVATE_H
diff --git a/src/libs/date/src/tz.cpp b/src/libs/date/src/tz.cpp
new file mode 100644
index 00000000..ad4e90e7
--- /dev/null
+++ b/src/libs/date/src/tz.cpp
@@ -0,0 +1,3825 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2015, 2016, 2017 Howard Hinnant
+// Copyright (c) 2015 Ville Voutilainen
+// Copyright (c) 2016 Alexander Kormanovsky
+// Copyright (c) 2016, 2017 Jiangang Zhuang
+// Copyright (c) 2017 Nicolas Veloz Savino
+// Copyright (c) 2017 Florian Dang
+// Copyright (c) 2017 Aaron Bishop
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// Our apologies.  When the previous paragraph was written, lowercase had not yet
+// been invented (that would involve another several millennia of evolution).
+// We did not mean to shout.
+
+#ifdef _WIN32
+   // windows.h will be included directly and indirectly (e.g. by curl).
+   // We need to define these macros to prevent windows.h bringing in
+   // more than we need and do it early so windows.h doesn't get included
+   // without these macros having been defined.
+   // min/max macros interfere with the C++ versions.
+#  ifndef NOMINMAX
+#    define NOMINMAX
+#  endif
+   // We don't need all that Windows has to offer.
+#  ifndef WIN32_LEAN_AND_MEAN
+#    define WIN32_LEAN_AND_MEAN
+#  endif
+
+   // for wcstombs
+#  ifndef _CRT_SECURE_NO_WARNINGS
+#    define _CRT_SECURE_NO_WARNINGS
+#  endif
+
+   // None of this happens with the MS SDK (at least VS14 which I tested), but:
+   // Compiling with mingw, we get "error: 'KF_FLAG_DEFAULT' was not declared in this scope."
+   // and error: 'SHGetKnownFolderPath' was not declared in this scope.".
+   // It seems when using mingw NTDDI_VERSION is undefined and that
+   // causes KNOWN_FOLDER_FLAG and the KF_ flags to not get defined.
+   // So we must define NTDDI_VERSION to get those flags on mingw.
+   // The docs say though here:
+   // https://msdn.microsoft.com/en-nz/library/windows/desktop/aa383745(v=vs.85).aspx
+   // that "If you define NTDDI_VERSION, you must also define _WIN32_WINNT."
+   // So we declare we require Vista or greater.
+#  ifdef __MINGW32__
+
+#    ifndef NTDDI_VERSION
+#      define NTDDI_VERSION 0x06000000
+#      define _WIN32_WINNT _WIN32_WINNT_VISTA
+#    elif NTDDI_VERSION < 0x06000000
+#      warning "If this fails to compile NTDDI_VERSION may be to low. See comments above."
+#    endif
+     // But once we define the values above we then get this linker error:
+     // "tz.cpp:(.rdata$.refptr.FOLDERID_Downloads[.refptr.FOLDERID_Downloads]+0x0): "
+     //     "undefined reference to `FOLDERID_Downloads'"
+     // which #include <initguid.h> cures see:
+     // https://support.microsoft.com/en-us/kb/130869
+#    include <initguid.h>
+     // But with <initguid.h> included, the error moves on to:
+     // error: 'FOLDERID_Downloads' was not declared in this scope
+     // Which #include <knownfolders.h> cures.
+#    include <knownfolders.h>
+
+#  endif  // __MINGW32__
+
+#  include <windows.h>
+#endif  // _WIN32
+
+#include "date/tz_private.h"
+
+#ifdef __APPLE__
+#  include "date/ios.h"
+#else
+#  define TARGET_OS_IPHONE 0
+#endif
+
+#if USE_OS_TZDB
+#  include <dirent.h>
+#endif
+#include <algorithm>
+#include <cctype>
+#include <cstdlib>
+#include <cstring>
+#include <cwchar>
+#include <exception>
+#include <fstream>
+#include <iostream>
+#include <iterator>
+#include <memory>
+#if USE_OS_TZDB
+#  include <queue>
+#endif
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <vector>
+#include <sys/stat.h>
+
+// unistd.h is used on some platforms as part of the the means to get
+// the current time zone. On Win32 windows.h provides a means to do it.
+// gcc/mingw supports unistd.h on Win32 but MSVC does not.
+
+#ifdef _WIN32
+#  ifdef WINAPI_FAMILY
+#    include <winapifamily.h>
+#    if WINAPI_FAMILY != WINAPI_FAMILY_DESKTOP_APP
+#      define WINRT
+#      define INSTALL .
+#    endif
+#  endif
+
+#  include <io.h> // _unlink etc.
+
+#  if defined(__clang__)
+    struct IUnknown;    // fix for issue with static_cast<> in objbase.h
+                        //   (see https://github.com/philsquared/Catch/issues/690)
+#  endif
+
+#  include <shlobj.h> // CoTaskFree, ShGetKnownFolderPath etc.
+#  if HAS_REMOTE_API
+#    include <direct.h> // _mkdir
+#    include <shellapi.h> // ShFileOperation etc.
+#  endif  // HAS_REMOTE_API
+#else   // !_WIN32
+#  include <unistd.h>
+#  if !USE_OS_TZDB
+#    include <wordexp.h>
+#  endif
+#  include <limits.h>
+#  include <string.h>
+#  if !USE_SHELL_API
+#    include <sys/stat.h>
+#    include <sys/fcntl.h>
+#    include <dirent.h>
+#    include <cstring>
+#    include <sys/wait.h>
+#    include <sys/types.h>
+#  endif //!USE_SHELL_API
+#endif  // !_WIN32
+
+
+#if HAS_REMOTE_API
+   // Note curl includes windows.h so we must include curl AFTER definitions of things
+   // that affect windows.h such as NOMINMAX.
+#if defined(_MSC_VER) && defined(SHORTENED_CURL_INCLUDE)
+   // For rmt_curl nuget package
+#  include <curl.h>
+#else
+#  include <curl/curl.h>
+#endif
+#endif
+
+#ifdef _WIN32
+static CONSTDATA char folder_delimiter = '\\';
+#else   // !_WIN32
+static CONSTDATA char folder_delimiter = '/';
+#endif  // !_WIN32
+
+#if defined(__GNUC__) && __GNUC__ < 5
+   // GCC 4.9 Bug 61489 Wrong warning with -Wmissing-field-initializers
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wmissing-field-initializers"
+#endif  // defined(__GNUC__) && __GNUC__ < 5
+
+#if !USE_OS_TZDB
+
+#  ifdef _WIN32
+#    ifndef WINRT
+
+namespace
+{
+    struct task_mem_deleter
+    {
+        void operator()(wchar_t buf[])
+        {
+            if (buf != nullptr)
+                CoTaskMemFree(buf);
+        }
+    };
+    using co_task_mem_ptr = std::unique_ptr<wchar_t[], task_mem_deleter>;
+}
+
+// We might need to know certain locations even if not using the remote API,
+// so keep these routines out of that block for now.
+static
+std::string
+get_known_folder(const GUID& folderid)
+{
+    std::string folder;
+    PWSTR pfolder = nullptr;
+    HRESULT hr = SHGetKnownFolderPath(folderid, KF_FLAG_DEFAULT, nullptr, &pfolder);
+    if (SUCCEEDED(hr))
+    {
+        co_task_mem_ptr folder_ptr(pfolder);
+        const wchar_t* fptr = folder_ptr.get();
+        auto state = std::mbstate_t();
+        const auto required = std::wcsrtombs(nullptr, &fptr, 0, &state);
+        if (required != 0 && required != std::size_t(-1))
+        {
+            folder.resize(required);
+            std::wcsrtombs(&folder[0], &fptr, folder.size(), &state);
+        }
+    }
+    return folder;
+}
+
+#      ifndef INSTALL
+
+// Usually something like "c:\Users\username\Downloads".
+static
+std::string
+get_download_folder()
+{
+    return get_known_folder(FOLDERID_Downloads);
+}
+
+#      endif  // !INSTALL
+
+#    endif // WINRT
+#  else // !_WIN32
+
+#    if !defined(INSTALL)
+
+static
+std::string
+expand_path(std::string path)
+{
+#      if TARGET_OS_IPHONE
+    return date::iOSUtils::get_tzdata_path();
+#      else  // !TARGET_OS_IPHONE
+    ::wordexp_t w{};
+    std::unique_ptr<::wordexp_t, void(*)(::wordexp_t*)> hold{&w, ::wordfree};
+    ::wordexp(path.c_str(), &w, 0);
+    if (w.we_wordc != 1)
+        throw std::runtime_error("Cannot expand path: " + path);
+    path = w.we_wordv[0];
+    return path;
+#      endif  // !TARGET_OS_IPHONE
+}
+
+static
+std::string
+get_download_folder()
+{
+    return expand_path("~/Downloads");
+}
+
+#    endif // !defined(INSTALL)
+
+#  endif  // !_WIN32
+
+#endif  // !USE_OS_TZDB
+
+namespace date
+{
+// +---------------------+
+// | Begin Configuration |
+// +---------------------+
+
+using namespace detail;
+
+#if !USE_OS_TZDB
+
+static
+std::string&
+access_install()
+{
+    static std::string install
+#ifndef INSTALL
+
+    = get_download_folder() + folder_delimiter + "tzdata";
+
+#else   // !INSTALL
+
+#  define STRINGIZEIMP(x) #x
+#  define STRINGIZE(x) STRINGIZEIMP(x)
+
+    = STRINGIZE(INSTALL) + std::string(1, folder_delimiter) + "tzdata";
+
+    #undef STRINGIZEIMP
+    #undef STRINGIZE
+#endif  // !INSTALL
+
+    return install;
+}
+
+void
+set_install(const std::string& s)
+{
+    access_install() = s;
+}
+
+static
+const std::string&
+get_install()
+{
+    static const std::string& ref = access_install();
+    return ref;
+}
+
+#if HAS_REMOTE_API
+static
+std::string
+get_download_gz_file(const std::string& version)
+{
+    auto file = get_install() + version + ".tar.gz";
+    return file;
+}
+#endif  // HAS_REMOTE_API
+
+#endif  // !USE_OS_TZDB
+
+// These can be used to reduce the range of the database to save memory
+CONSTDATA auto min_year = date::year::min();
+CONSTDATA auto max_year = date::year::max();
+
+CONSTDATA auto min_day = date::January/1;
+CONSTDATA auto max_day = date::December/31;
+
+#if USE_OS_TZDB
+
+CONSTCD14 const sys_seconds min_seconds = sys_days(min_year/min_day);
+
+#endif  // USE_OS_TZDB
+
+#ifndef _WIN32
+
+static
+std::string
+discover_tz_dir()
+{
+    struct stat sb;
+    using namespace std;
+#  ifndef __APPLE__
+    CONSTDATA auto tz_dir_default = "/usr/share/zoneinfo";
+    CONSTDATA auto tz_dir_buildroot = "/usr/share/zoneinfo/uclibc";
+
+    // Check special path which is valid for buildroot with uclibc builds
+    if(stat(tz_dir_buildroot, &sb) == 0 && S_ISDIR(sb.st_mode))
+        return tz_dir_buildroot;
+    else if(stat(tz_dir_default, &sb) == 0 && S_ISDIR(sb.st_mode))
+        return tz_dir_default;
+    else
+        throw runtime_error("discover_tz_dir failed to find zoneinfo\n");
+#  else  // __APPLE__
+#      if TARGET_OS_IPHONE
+    return "/var/db/timezone/zoneinfo";
+#      else
+    CONSTDATA auto timezone = "/etc/localtime";
+    if (!(lstat(timezone, &sb) == 0 && S_ISLNK(sb.st_mode) && sb.st_size > 0))
+        throw runtime_error("discover_tz_dir failed\n");
+    string result;
+    char rp[PATH_MAX+1] = {};
+    if (readlink(timezone, rp, sizeof(rp)-1) > 0)
+        result = string(rp);
+    else
+        throw system_error(errno, system_category(), "readlink() failed");
+    auto i = result.find("zoneinfo");
+    if (i == string::npos)
+        throw runtime_error("discover_tz_dir failed to find zoneinfo\n");
+    i = result.find('/', i);
+    if (i == string::npos)
+        throw runtime_error("discover_tz_dir failed to find '/'\n");
+    return result.substr(0, i);
+#      endif
+#  endif  // __APPLE__
+}
+
+static
+const std::string&
+get_tz_dir()
+{
+    static const std::string tz_dir = discover_tz_dir();
+    return tz_dir;
+}
+
+#endif
+
+// +-------------------+
+// | End Configuration |
+// +-------------------+
+
+#ifndef _MSC_VER
+static_assert(min_year <= max_year, "Configuration error");
+#endif
+
+static std::unique_ptr<tzdb> init_tzdb();
+
+tzdb_list::~tzdb_list()
+{
+    const tzdb* ptr = head_;
+    head_ = nullptr;
+    while (ptr != nullptr)
+    {
+        auto next = ptr->next;
+        delete ptr;
+        ptr = next;
+    }
+}
+
+tzdb_list::tzdb_list(tzdb_list&& x) noexcept
+   : head_{x.head_.exchange(nullptr)}
+{
+}
+
+void
+tzdb_list::push_front(tzdb* tzdb) noexcept
+{
+    tzdb->next = head_;
+    head_ = tzdb;
+}
+
+tzdb_list::const_iterator
+tzdb_list::erase_after(const_iterator p) noexcept
+{
+    auto t = p.p_->next;
+    p.p_->next = p.p_->next->next;
+    delete t;
+    return ++p;
+}
+
+struct tzdb_list::undocumented_helper
+{
+    static void push_front(tzdb_list& db_list, tzdb* tzdb) noexcept
+    {
+        db_list.push_front(tzdb);
+    }
+};
+
+static
+tzdb_list
+create_tzdb()
+{
+    tzdb_list tz_db;
+    tzdb_list::undocumented_helper::push_front(tz_db, init_tzdb().release());
+    return tz_db;
+}
+
+tzdb_list&
+get_tzdb_list()
+{
+    static tzdb_list tz_db = create_tzdb();
+    return tz_db;
+}
+
+#if !USE_OS_TZDB
+
+#ifdef _WIN32
+
+static
+void
+sort_zone_mappings(std::vector<date::detail::timezone_mapping>& mappings)
+{
+    std::sort(mappings.begin(), mappings.end(),
+        [](const date::detail::timezone_mapping& lhs,
+           const date::detail::timezone_mapping& rhs)->bool
+    {
+        auto other_result = lhs.other.compare(rhs.other);
+        if (other_result < 0)
+            return true;
+        else if (other_result == 0)
+        {
+            auto territory_result = lhs.territory.compare(rhs.territory);
+            if (territory_result < 0)
+                return true;
+            else if (territory_result == 0)
+            {
+                if (lhs.type < rhs.type)
+                    return true;
+            }
+        }
+        return false;
+    });
+}
+
+static
+bool
+native_to_standard_timezone_name(const std::string& native_tz_name,
+                                 std::string& standard_tz_name)
+{
+    // TOOD! Need be a case insensitive compare?
+    if (native_tz_name == "UTC")
+    {
+        standard_tz_name = "Etc/UTC";
+        return true;
+    }
+    standard_tz_name.clear();
+    // TODO! we can improve on linear search.
+    const auto& mappings = date::get_tzdb().mappings;
+    for (const auto& tzm : mappings)
+    {
+        if (tzm.other == native_tz_name)
+        {
+            standard_tz_name = tzm.type;
+            return true;
+        }
+    }
+    return false;
+}
+
+// Parse this XML file:
+// https://raw.githubusercontent.com/unicode-org/cldr/master/common/supplemental/windowsZones.xml
+// The parsing method is designed to be simple and quick. It is not overly
+// forgiving of change but it should diagnose basic format issues.
+// See timezone_mapping structure for more info.
+static
+std::vector<detail::timezone_mapping>
+load_timezone_mappings_from_xml_file(const std::string& input_path)
+{
+    std::size_t line_num = 0;
+    std::vector<detail::timezone_mapping> mappings;
+    std::string line;
+
+    std::ifstream is(input_path);
+    if (!is.is_open())
+    {
+        // We don't emit file exceptions because that's an implementation detail.
+        std::string msg = "Error opening time zone mapping file \"";
+        msg += input_path;
+        msg += "\".";
+        throw std::runtime_error(msg);
+    }
+
+    auto error = [&input_path, &line_num](const char* info)
+    {
+        std::string msg = "Error loading time zone mapping file \"";
+        msg += input_path;
+        msg += "\" at line ";
+        msg += std::to_string(line_num);
+        msg += ": ";
+        msg += info;
+        throw std::runtime_error(msg);
+    };
+    // [optional space]a="b"
+    auto read_attribute = [&line, &error]
+                          (const char* name, std::string& value, std::size_t startPos)
+                          ->std::size_t
+    {
+        value.clear();
+        // Skip leading space before attribute name.
+        std::size_t spos = line.find_first_not_of(' ', startPos);
+        if (spos == std::string::npos)
+            spos = startPos;
+        // Assume everything up to next = is the attribute name
+        // and that an = will always delimit that.
+        std::size_t epos = line.find('=', spos);
+        if (epos == std::string::npos)
+            error("Expected \'=\' right after attribute name.");
+        std::size_t name_len = epos - spos;
+        // Expect the name we find matches the name we expect.
+        if (line.compare(spos, name_len, name) != 0)
+        {
+            std::string msg;
+            msg = "Expected attribute name \'";
+            msg += name;
+            msg += "\' around position ";
+            msg += std::to_string(spos);
+            msg += " but found something else.";
+            error(msg.c_str());
+        }
+        ++epos; // Skip the '=' that is after the attribute name.
+        spos = epos;
+        if (spos < line.length() && line[spos] == '\"')
+            ++spos; // Skip the quote that is before the attribute value.
+        else
+        {
+            std::string msg = "Expected '\"' to begin value of attribute \'";
+            msg += name;
+            msg += "\'.";
+            error(msg.c_str());
+        }
+        epos = line.find('\"', spos);
+        if (epos == std::string::npos)
+        {
+            std::string msg = "Expected '\"' to end value of attribute \'";
+            msg += name;
+            msg += "\'.";
+            error(msg.c_str());
+        }
+        // Extract everything in between the quotes. Note no escaping is done.
+        std::size_t value_len = epos - spos;
+        value.assign(line, spos, value_len);
+        ++epos; // Skip the quote that is after the attribute value;
+        return epos;
+    };
+
+    // Quick but not overly forgiving XML mapping file processing.
+    bool mapTimezonesOpenTagFound = false;
+    bool mapTimezonesCloseTagFound = false;
+    std::size_t mapZonePos = std::string::npos;
+    std::size_t mapTimezonesPos = std::string::npos;
+    CONSTDATA char mapTimeZonesOpeningTag[] = { "<mapTimezones " };
+    CONSTDATA char mapZoneOpeningTag[] = { "<mapZone " };
+    CONSTDATA std::size_t mapZoneOpeningTagLen = sizeof(mapZoneOpeningTag) /
+                                                 sizeof(mapZoneOpeningTag[0]) - 1;
+    while (!mapTimezonesOpenTagFound)
+    {
+        std::getline(is, line);
+        ++line_num;
+        if (is.eof())
+        {
+            // If there is no mapTimezones tag is it an error?
+            // Perhaps if there are no mapZone mappings it might be ok for
+            // its parent mapTimezones element to be missing?
+            // We treat this as an error though on the assumption that if there
+            // really are no mappings we should still get a mapTimezones parent
+            // element but no mapZone elements inside. Assuming we must
+            // find something will hopefully at least catch more drastic formatting
+            // changes or errors than if we don't do this and assume nothing found.
+            error("Expected a mapTimezones opening tag.");
+        }
+        mapTimezonesPos = line.find(mapTimeZonesOpeningTag);
+        mapTimezonesOpenTagFound = (mapTimezonesPos != std::string::npos);
+    }
+
+    // NOTE: We could extract the version info that follows the opening
+    // mapTimezones tag and compare that to the version of other data we have.
+    // I would have expected them to be kept in synch but testing has shown
+    // it typically does not match anyway. So what's the point?
+    while (!mapTimezonesCloseTagFound)
+    {
+        std::ws(is);
+        std::getline(is, line);
+        ++line_num;
+        if (is.eof())
+            error("Expected a mapTimezones closing tag.");
+        if (line.empty())
+            continue;
+        mapZonePos = line.find(mapZoneOpeningTag);
+        if (mapZonePos != std::string::npos)
+        {
+            mapZonePos += mapZoneOpeningTagLen;
+            detail::timezone_mapping zm{};
+            std::size_t pos = read_attribute("other", zm.other, mapZonePos);
+            pos = read_attribute("territory", zm.territory, pos);
+            read_attribute("type", zm.type, pos);
+            mappings.push_back(std::move(zm));
+
+            continue;
+        }
+        mapTimezonesPos = line.find("</mapTimezones>");
+        mapTimezonesCloseTagFound = (mapTimezonesPos != std::string::npos);
+        if (!mapTimezonesCloseTagFound)
+        {
+            std::size_t commentPos = line.find("<!--");
+            if (commentPos == std::string::npos)
+                error("Unexpected mapping record found. A xml mapZone or comment "
+                      "attribute or mapTimezones closing tag was expected.");
+        }
+    }
+
+    is.close();
+    return mappings;
+}
+
+#endif  // _WIN32
+
+// Parsing helpers
+
+static
+std::string
+parse3(std::istream& in)
+{
+    std::string r(3, ' ');
+    ws(in);
+    r[0] = static_cast<char>(in.get());
+    r[1] = static_cast<char>(in.get());
+    r[2] = static_cast<char>(in.get());
+    return r;
+}
+
+static
+unsigned
+parse_dow(std::istream& in)
+{
+    CONSTDATA char*const dow_names[] =
+        {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
+    auto s = parse3(in);
+    auto dow = std::find(std::begin(dow_names), std::end(dow_names), s) - dow_names;
+    if (dow >= std::end(dow_names) - std::begin(dow_names))
+        throw std::runtime_error("oops: bad dow name: " + s);
+    return static_cast<unsigned>(dow);
+}
+
+static
+unsigned
+parse_month(std::istream& in)
+{
+    CONSTDATA char*const month_names[] =
+        {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
+         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
+    auto s = parse3(in);
+    auto m = std::find(std::begin(month_names), std::end(month_names), s) - month_names;
+    if (m >= std::end(month_names) - std::begin(month_names))
+        throw std::runtime_error("oops: bad month name: " + s);
+    return static_cast<unsigned>(++m);
+}
+
+static
+std::chrono::seconds
+parse_unsigned_time(std::istream& in)
+{
+    using namespace std::chrono;
+    int x;
+    in >> x;
+    auto r = seconds{hours{x}};
+    if (!in.eof() && in.peek() == ':')
+    {
+        in.get();
+        in >> x;
+        r += minutes{x};
+        if (!in.eof() && in.peek() == ':')
+        {
+            in.get();
+            in >> x;
+            r += seconds{x};
+        }
+    }
+    return r;
+}
+
+static
+std::chrono::seconds
+parse_signed_time(std::istream& in)
+{
+    ws(in);
+    auto sign = 1;
+    if (in.peek() == '-')
+    {
+        sign = -1;
+        in.get();
+    }
+    else if (in.peek() == '+')
+        in.get();
+    return sign * parse_unsigned_time(in);
+}
+
+// MonthDayTime
+
+detail::MonthDayTime::MonthDayTime(local_seconds tp, tz timezone)
+    : zone_(timezone)
+{
+    using namespace date;
+    const auto dp = date::floor<days>(tp);
+    const auto hms = make_time(tp - dp);
+    const auto ymd = year_month_day(dp);
+    u = ymd.month() / ymd.day();
+    h_ = hms.hours();
+    m_ = hms.minutes();
+    s_ = hms.seconds();
+}
+
+detail::MonthDayTime::MonthDayTime(const date::month_day& md, tz timezone)
+    : zone_(timezone)
+{
+    u = md;
+}
+
+date::day
+detail::MonthDayTime::day() const
+{
+    switch (type_)
+    {
+    case month_day:
+        return u.month_day_.day();
+    case month_last_dow:
+        return date::day{31};
+    case lteq:
+    case gteq:
+        break;
+    }
+    return u.month_day_weekday_.month_day_.day();
+}
+
+date::month
+detail::MonthDayTime::month() const
+{
+    switch (type_)
+    {
+    case month_day:
+        return u.month_day_.month();
+    case month_last_dow:
+        return u.month_weekday_last_.month();
+    case lteq:
+    case gteq:
+        break;
+    }
+    return u.month_day_weekday_.month_day_.month();
+}
+
+int
+detail::MonthDayTime::compare(date::year y, const MonthDayTime& x, date::year yx,
+                      std::chrono::seconds offset, std::chrono::minutes prev_save) const
+{
+    if (zone_ != x.zone_)
+    {
+        auto dp0 = to_sys_days(y);
+        auto dp1 = x.to_sys_days(yx);
+        if (std::abs((dp0-dp1).count()) > 1)
+            return dp0 < dp1 ? -1 : 1;
+        if (zone_ == tz::local)
+        {
+            auto tp0 = to_time_point(y) - prev_save;
+            if (x.zone_ == tz::utc)
+                tp0 -= offset;
+            auto tp1 = x.to_time_point(yx);
+            return tp0 < tp1 ? -1 : tp0 == tp1 ? 0 : 1;
+        }
+        else if (zone_ == tz::standard)
+        {
+            auto tp0 = to_time_point(y);
+            auto tp1 = x.to_time_point(yx);
+            if (x.zone_ == tz::local)
+                tp1 -= prev_save;
+            else
+                tp0 -= offset;
+            return tp0 < tp1 ? -1 : tp0 == tp1 ? 0 : 1;
+        }
+        // zone_ == tz::utc
+        auto tp0 = to_time_point(y);
+        auto tp1 = x.to_time_point(yx);
+        if (x.zone_ == tz::local)
+            tp1 -= offset + prev_save;
+        else
+            tp1 -= offset;
+        return tp0 < tp1 ? -1 : tp0 == tp1 ? 0 : 1;
+    }
+    auto const t0 = to_time_point(y);
+    auto const t1 = x.to_time_point(yx);
+    return t0 < t1 ? -1 : t0 == t1 ? 0 : 1;
+}
+
+sys_seconds
+detail::MonthDayTime::to_sys(date::year y, std::chrono::seconds offset,
+                     std::chrono::seconds save) const
+{
+    using namespace date;
+    using namespace std::chrono;
+    auto until_utc = to_time_point(y);
+    if (zone_ == tz::standard)
+        until_utc -= offset;
+    else if (zone_ == tz::local)
+        until_utc -= offset + save;
+    return until_utc;
+}
+
+detail::MonthDayTime::U&
+detail::MonthDayTime::U::operator=(const date::month_day& x)
+{
+    month_day_ = x;
+    return *this;
+}
+
+detail::MonthDayTime::U&
+detail::MonthDayTime::U::operator=(const date::month_weekday_last& x)
+{
+    month_weekday_last_ = x;
+    return *this;
+}
+
+detail::MonthDayTime::U&
+detail::MonthDayTime::U::operator=(const pair& x)
+{
+    month_day_weekday_ = x;
+    return *this;
+}
+
+date::sys_days
+detail::MonthDayTime::to_sys_days(date::year y) const
+{
+    using namespace std::chrono;
+    using namespace date;
+    switch (type_)
+    {
+    case month_day:
+        return sys_days(y/u.month_day_);
+    case month_last_dow:
+        return sys_days(y/u.month_weekday_last_);
+    case lteq:
+        {
+            auto const x = y/u.month_day_weekday_.month_day_;
+            auto const wd1 = weekday(static_cast<sys_days>(x));
+            auto const wd0 = u.month_day_weekday_.weekday_;
+            return sys_days(x) - (wd1-wd0);
+        }
+    case gteq:
+        break;
+    }
+    auto const x = y/u.month_day_weekday_.month_day_;
+    auto const wd1 = u.month_day_weekday_.weekday_;
+    auto const wd0 = weekday(static_cast<sys_days>(x));
+    return sys_days(x) + (wd1-wd0);
+}
+
+sys_seconds
+detail::MonthDayTime::to_time_point(date::year y) const
+{
+    // Add seconds first to promote to largest rep early to prevent overflow
+    return to_sys_days(y) + s_ + h_ + m_;
+}
+
+void
+detail::MonthDayTime::canonicalize(date::year y)
+{
+    using namespace std::chrono;
+    using namespace date;
+    switch (type_)
+    {
+    case month_day:
+        return;
+    case month_last_dow:
+        {
+            auto const ymd = year_month_day(sys_days(y/u.month_weekday_last_));
+            u.month_day_ = ymd.month()/ymd.day();
+            type_ = month_day;
+            return;
+        }
+    case lteq:
+        {
+            auto const x = y/u.month_day_weekday_.month_day_;
+            auto const wd1 = weekday(static_cast<sys_days>(x));
+            auto const wd0 = u.month_day_weekday_.weekday_;
+            auto const ymd = year_month_day(sys_days(x) - (wd1-wd0));
+            u.month_day_ = ymd.month()/ymd.day();
+            type_ = month_day;
+            return;
+        }
+    case gteq:
+        {
+            auto const x = y/u.month_day_weekday_.month_day_;
+            auto const wd1 = u.month_day_weekday_.weekday_;
+            auto const wd0 = weekday(static_cast<sys_days>(x));
+            auto const ymd = year_month_day(sys_days(x) + (wd1-wd0));
+            u.month_day_ = ymd.month()/ymd.day();
+            type_ = month_day;
+            return;
+        }
+    }
+}
+
+std::istream&
+detail::operator>>(std::istream& is, MonthDayTime& x)
+{
+    using namespace date;
+    using namespace std::chrono;
+    assert(((std::ios::failbit | std::ios::badbit) & is.exceptions()) ==
+            (std::ios::failbit | std::ios::badbit));
+    x = MonthDayTime{};
+    if (!is.eof() && ws(is) && !is.eof() && is.peek() != '#')
+    {
+        auto m = parse_month(is);
+        if (!is.eof() && ws(is) && !is.eof() && is.peek() != '#')
+        {
+            if (is.peek() == 'l')
+            {
+                for (int i = 0; i < 4; ++i)
+                    is.get();
+                auto dow = parse_dow(is);
+                x.type_ = MonthDayTime::month_last_dow;
+                x.u = date::month(m)/weekday(dow)[last];
+            }
+            else if (std::isalpha(is.peek()))
+            {
+                auto dow = parse_dow(is);
+                char c{};
+                is >> c;
+                if (c == '<' || c == '>')
+                {
+                    char c2{};
+                    is >> c2;
+                    if (c2 != '=')
+                        throw std::runtime_error(std::string("bad operator: ") + c + c2);
+                    int d;
+                    is >> d;
+                    if (d < 1 || d > 31)
+                        throw std::runtime_error(std::string("bad operator: ") + c + c2
+                                 + std::to_string(d));
+                    x.type_ = c == '<' ? MonthDayTime::lteq : MonthDayTime::gteq;
+                    x.u = MonthDayTime::pair{ date::month(m) / d, date::weekday(dow) };
+                }
+                else
+                    throw std::runtime_error(std::string("bad operator: ") + c);
+            }
+            else  // if (std::isdigit(is.peek())
+            {
+                int d;
+                is >> d;
+                if (d < 1 || d > 31)
+                    throw std::runtime_error(std::string("day of month: ")
+                             + std::to_string(d));
+                x.type_ = MonthDayTime::month_day;
+                x.u = date::month(m)/d;
+            }
+            if (!is.eof() && ws(is) && !is.eof() && is.peek() != '#')
+            {
+                int t;
+                is >> t;
+                x.h_ = hours{t};
+                if (!is.eof() && is.peek() == ':')
+                {
+                    is.get();
+                    is >> t;
+                    x.m_ = minutes{t};
+                    if (!is.eof() && is.peek() == ':')
+                    {
+                        is.get();
+                        is >> t;
+                        x.s_ = seconds{t};
+                    }
+                }
+                if (!is.eof() && std::isalpha(is.peek()))
+                {
+                    char c;
+                    is >> c;
+                    switch (c)
+                    {
+                    case 's':
+                        x.zone_ = tz::standard;
+                        break;
+                    case 'u':
+                        x.zone_ = tz::utc;
+                        break;
+                    }
+                }
+            }
+        }
+        else
+        {
+            x.u = month{m}/1;
+        }
+    }
+    return is;
+}
+
+std::ostream&
+detail::operator<<(std::ostream& os, const MonthDayTime& x)
+{
+    switch (x.type_)
+    {
+    case MonthDayTime::month_day:
+        os << x.u.month_day_ << "                  ";
+        break;
+    case MonthDayTime::month_last_dow:
+        os << x.u.month_weekday_last_ << "           ";
+        break;
+    case MonthDayTime::lteq:
+        os << x.u.month_day_weekday_.weekday_ << " on or before "
+           << x.u.month_day_weekday_.month_day_ << "  ";
+        break;
+    case MonthDayTime::gteq:
+        if ((static_cast<unsigned>(x.day()) - 1) % 7 == 0)
+        {
+            os << (x.u.month_day_weekday_.month_day_.month() /
+                   x.u.month_day_weekday_.weekday_[
+                       (static_cast<unsigned>(x.day()) - 1)/7+1]) << "              ";
+        }
+        else
+        {
+            os << x.u.month_day_weekday_.weekday_ << " on or after "
+               << x.u.month_day_weekday_.month_day_ << "  ";
+        }
+        break;
+    }
+    os << date::make_time(x.s_ + x.h_ + x.m_);
+    if (x.zone_ == tz::utc)
+        os << "UTC   ";
+    else if (x.zone_ == tz::standard)
+        os << "STD   ";
+    else
+        os << "      ";
+    return os;
+}
+
+// Rule
+
+detail::Rule::Rule(const std::string& s)
+{
+    try
+    {
+        using namespace date;
+        using namespace std::chrono;
+        std::istringstream in(s);
+        in.exceptions(std::ios::failbit | std::ios::badbit);
+        std::string word;
+        in >> word >> name_;
+        int x;
+        ws(in);
+        if (std::isalpha(in.peek()))
+        {
+            in >> word;
+            if (word == "min")
+            {
+                starting_year_ = year::min();
+            }
+            else
+                throw std::runtime_error("Didn't find expected word: " + word);
+        }
+        else
+        {
+            in >> x;
+            starting_year_ = year{x};
+        }
+        std::ws(in);
+        if (std::isalpha(in.peek()))
+        {
+            in >> word;
+            if (word == "only")
+            {
+                ending_year_ = starting_year_;
+            }
+            else if (word == "max")
+            {
+                ending_year_ = year::max();
+            }
+            else
+                throw std::runtime_error("Didn't find expected word: " + word);
+        }
+        else
+        {
+            in >> x;
+            ending_year_ = year{x};
+        }
+        in >> word;  // TYPE (always "-")
+        assert(word == "-");
+        in >> starting_at_;
+        save_ = duration_cast<minutes>(parse_signed_time(in));
+        in >> abbrev_;
+        if (abbrev_ == "-")
+            abbrev_.clear();
+        assert(hours{-1} <= save_ && save_ <= hours{2});
+    }
+    catch (...)
+    {
+        std::cerr << s << '\n';
+        std::cerr << *this << '\n';
+        throw;
+    }
+}
+
+detail::Rule::Rule(const Rule& r, date::year starting_year, date::year ending_year)
+    : name_(r.name_)
+    , starting_year_(starting_year)
+    , ending_year_(ending_year)
+    , starting_at_(r.starting_at_)
+    , save_(r.save_)
+    , abbrev_(r.abbrev_)
+{
+}
+
+bool
+detail::operator==(const Rule& x, const Rule& y)
+{
+    if (std::tie(x.name_, x.save_, x.starting_year_, x.ending_year_) ==
+        std::tie(y.name_, y.save_, y.starting_year_, y.ending_year_))
+        return x.month() == y.month() && x.day() == y.day();
+    return false;
+}
+
+bool
+detail::operator<(const Rule& x, const Rule& y)
+{
+    using namespace std::chrono;
+    auto const xm = x.month();
+    auto const ym = y.month();
+    if (std::tie(x.name_, x.starting_year_, xm, x.ending_year_) <
+        std::tie(y.name_, y.starting_year_, ym, y.ending_year_))
+        return true;
+    if (std::tie(x.name_, x.starting_year_, xm, x.ending_year_) >
+        std::tie(y.name_, y.starting_year_, ym, y.ending_year_))
+        return false;
+    return x.day() < y.day();
+}
+
+bool
+detail::operator==(const Rule& x, const date::year& y)
+{
+    return x.starting_year_ <= y && y <= x.ending_year_;
+}
+
+bool
+detail::operator<(const Rule& x, const date::year& y)
+{
+    return x.ending_year_ < y;
+}
+
+bool
+detail::operator==(const date::year& x, const Rule& y)
+{
+    return y.starting_year_ <= x && x <= y.ending_year_;
+}
+
+bool
+detail::operator<(const date::year& x, const Rule& y)
+{
+    return x < y.starting_year_;
+}
+
+bool
+detail::operator==(const Rule& x, const std::string& y)
+{
+    return x.name() == y;
+}
+
+bool
+detail::operator<(const Rule& x, const std::string& y)
+{
+    return x.name() < y;
+}
+
+bool
+detail::operator==(const std::string& x, const Rule& y)
+{
+    return y.name() == x;
+}
+
+bool
+detail::operator<(const std::string& x, const Rule& y)
+{
+    return x < y.name();
+}
+
+std::ostream&
+detail::operator<<(std::ostream& os, const Rule& r)
+{
+    using namespace date;
+    using namespace std::chrono;
+    detail::save_ostream<char> _(os);
+    os.fill(' ');
+    os.flags(std::ios::dec | std::ios::left);
+    os.width(15);
+    os << r.name_;
+    os << r.starting_year_ << "    " << r.ending_year_ << "    ";
+    os << r.starting_at_;
+    if (r.save_ >= minutes{0})
+        os << ' ';
+    os << date::make_time(r.save_) << "   ";
+    os << r.abbrev_;
+    return os;
+}
+
+date::day
+detail::Rule::day() const
+{
+    return starting_at_.day();
+}
+
+date::month
+detail::Rule::month() const
+{
+    return starting_at_.month();
+}
+
+struct find_rule_by_name
+{
+    bool operator()(const Rule& x, const std::string& nm) const
+    {
+        return x.name() < nm;
+    }
+
+    bool operator()(const std::string& nm, const Rule& x) const
+    {
+        return nm < x.name();
+    }
+};
+
+bool
+detail::Rule::overlaps(const Rule& x, const Rule& y)
+{
+    // assume x.starting_year_ <= y.starting_year_;
+    if (!(x.starting_year_ <= y.starting_year_))
+    {
+        std::cerr << x << '\n';
+        std::cerr << y << '\n';
+        assert(x.starting_year_ <= y.starting_year_);
+    }
+    if (y.starting_year_ > x.ending_year_)
+        return false;
+    return !(x.starting_year_ == y.starting_year_ && x.ending_year_ == y.ending_year_);
+}
+
+void
+detail::Rule::split(std::vector<Rule>& rules, std::size_t i, std::size_t k, std::size_t& e)
+{
+    using namespace date;
+    using difference_type = std::vector<Rule>::iterator::difference_type;
+    // rules[i].starting_year_ <= rules[k].starting_year_ &&
+    //     rules[i].ending_year_ >= rules[k].starting_year_ &&
+    //     (rules[i].starting_year_ != rules[k].starting_year_ ||
+    //      rules[i].ending_year_ != rules[k].ending_year_)
+    assert(rules[i].starting_year_ <= rules[k].starting_year_ &&
+           rules[i].ending_year_ >= rules[k].starting_year_ &&
+           (rules[i].starting_year_ != rules[k].starting_year_ ||
+            rules[i].ending_year_ != rules[k].ending_year_));
+    if (rules[i].starting_year_ == rules[k].starting_year_)
+    {
+        if (rules[k].ending_year_ < rules[i].ending_year_)
+        {
+            rules.insert(rules.begin() + static_cast<difference_type>(k+1),
+                         Rule(rules[i], rules[k].ending_year_ + years{1},
+                              std::move(rules[i].ending_year_)));
+            ++e;
+            rules[i].ending_year_ = rules[k].ending_year_;
+        }
+        else  // rules[k].ending_year_ > rules[i].ending_year_
+        {
+            rules.insert(rules.begin() + static_cast<difference_type>(k+1),
+                         Rule(rules[k], rules[i].ending_year_ + years{1},
+                              std::move(rules[k].ending_year_)));
+            ++e;
+            rules[k].ending_year_ = rules[i].ending_year_;
+        }
+    }
+    else  // rules[i].starting_year_ < rules[k].starting_year_
+    {
+        if (rules[k].ending_year_ < rules[i].ending_year_)
+        {
+            rules.insert(rules.begin() + static_cast<difference_type>(k),
+                         Rule(rules[i], rules[k].starting_year_, rules[k].ending_year_));
+            ++k;
+            rules.insert(rules.begin() + static_cast<difference_type>(k+1),
+                         Rule(rules[i], rules[k].ending_year_ + years{1},
+                              std::move(rules[i].ending_year_)));
+            rules[i].ending_year_ = rules[k].starting_year_ - years{1};
+            e += 2;
+        }
+        else if (rules[k].ending_year_ > rules[i].ending_year_)
+        {
+            rules.insert(rules.begin() + static_cast<difference_type>(k),
+                         Rule(rules[i], rules[k].starting_year_, rules[i].ending_year_));
+            ++k;
+            rules.insert(rules.begin() + static_cast<difference_type>(k+1),
+                         Rule(rules[k], rules[i].ending_year_ + years{1},
+                         std::move(rules[k].ending_year_)));
+            e += 2;
+            rules[k].ending_year_ = std::move(rules[i].ending_year_);
+            rules[i].ending_year_ = rules[k].starting_year_ - years{1};
+        }
+        else  // rules[k].ending_year_ == rules[i].ending_year_
+        {
+            rules.insert(rules.begin() + static_cast<difference_type>(k),
+                         Rule(rules[i], rules[k].starting_year_,
+                         std::move(rules[i].ending_year_)));
+            ++k;
+            ++e;
+            rules[i].ending_year_ = rules[k].starting_year_ - years{1};
+        }
+    }
+}
+
+void
+detail::Rule::split_overlaps(std::vector<Rule>& rules, std::size_t i, std::size_t& e)
+{
+    using difference_type = std::vector<Rule>::iterator::difference_type;
+    auto j = i;
+    for (; i + 1 < e; ++i)
+    {
+        for (auto k = i + 1; k < e; ++k)
+        {
+            if (overlaps(rules[i], rules[k]))
+            {
+                split(rules, i, k, e);
+                std::sort(rules.begin() + static_cast<difference_type>(i),
+                          rules.begin() + static_cast<difference_type>(e));
+            }
+        }
+    }
+    for (; j < e; ++j)
+    {
+        if (rules[j].starting_year() == rules[j].ending_year())
+            rules[j].starting_at_.canonicalize(rules[j].starting_year());
+    }
+}
+
+void
+detail::Rule::split_overlaps(std::vector<Rule>& rules)
+{
+    using difference_type = std::vector<Rule>::iterator::difference_type;
+    for (std::size_t i = 0; i < rules.size();)
+    {
+        auto e = static_cast<std::size_t>(std::upper_bound(
+            rules.cbegin()+static_cast<difference_type>(i), rules.cend(), rules[i].name(),
+            [](const std::string& nm, const Rule& x)
+            {
+                return nm < x.name();
+            }) - rules.cbegin());
+        split_overlaps(rules, i, e);
+        auto first_rule = rules.begin() + static_cast<difference_type>(i);
+        auto last_rule = rules.begin() + static_cast<difference_type>(e);
+        auto t = std::lower_bound(first_rule, last_rule, min_year);
+        if (t > first_rule+1)
+        {
+            if (t == last_rule || t->starting_year() >= min_year)
+                --t;
+            auto d = static_cast<std::size_t>(t - first_rule);
+            rules.erase(first_rule, t);
+            e -= d;
+        }
+        first_rule = rules.begin() + static_cast<difference_type>(i);
+        last_rule = rules.begin() + static_cast<difference_type>(e);
+        t = std::upper_bound(first_rule, last_rule, max_year);
+        if (t != last_rule)
+        {
+            auto d = static_cast<std::size_t>(last_rule - t);
+            rules.erase(t, last_rule);
+            e -= d;
+        }
+        i = e;
+    }
+    rules.shrink_to_fit();
+}
+
+// Find the rule that comes chronologically before Rule r.  For multi-year rules,
+// y specifies which rules in r.  For single year rules, y is assumed to be equal
+// to the year specified by r.
+// Returns a pointer to the chronologically previous rule, and the year within
+// that rule.  If there is no previous rule, returns nullptr and year::min().
+// Preconditions:
+//     r->starting_year() <= y && y <= r->ending_year()
+static
+std::pair<const Rule*, date::year>
+find_previous_rule(const Rule* r, date::year y)
+{
+    using namespace date;
+    auto const& rules = get_tzdb().rules;
+    if (y == r->starting_year())
+    {
+        if (r == &rules.front() || r->name() != r[-1].name())
+            std::terminate();  // never called with first rule
+        --r;
+        if (y == r->starting_year())
+            return {r, y};
+        return {r, r->ending_year()};
+    }
+    if (r == &rules.front() || r->name() != r[-1].name() ||
+        r[-1].starting_year() < r->starting_year())
+    {
+        while (r < &rules.back() && r->name() == r[1].name() &&
+               r->starting_year() == r[1].starting_year())
+            ++r;
+        return {r, --y};
+    }
+    --r;
+    return {r, y};
+}
+
+// Find the rule that comes chronologically after Rule r.  For multi-year rules,
+// y specifies which rules in r.  For single year rules, y is assumed to be equal
+// to the year specified by r.
+// Returns a pointer to the chronologically next rule, and the year within
+// that rule.  If there is no next rule, return a pointer to a defaulted rule
+// and y+1.
+// Preconditions:
+//     first <= r && r < last && r->starting_year() <= y && y <= r->ending_year()
+//     [first, last) all have the same name
+static
+std::pair<const Rule*, date::year>
+find_next_rule(const Rule* first_rule, const Rule* last_rule, const Rule* r, date::year y)
+{
+    using namespace date;
+    if (y == r->ending_year())
+    {
+        if (r == last_rule-1)
+            return {nullptr, year::max()};
+        ++r;
+        if (y == r->ending_year())
+            return {r, y};
+        return {r, r->starting_year()};
+    }
+    if (r == last_rule-1 || r->ending_year() < r[1].ending_year())
+    {
+        while (r > first_rule && r->starting_year() == r[-1].starting_year())
+            --r;
+        return {r, ++y};
+    }
+    ++r;
+    return {r, y};
+}
+
+// Find the rule that comes chronologically after Rule r.  For multi-year rules,
+// y specifies which rules in r.  For single year rules, y is assumed to be equal
+// to the year specified by r.
+// Returns a pointer to the chronologically next rule, and the year within
+// that rule.  If there is no next rule, return nullptr and year::max().
+// Preconditions:
+//     r->starting_year() <= y && y <= r->ending_year()
+static
+std::pair<const Rule*, date::year>
+find_next_rule(const Rule* r, date::year y)
+{
+    using namespace date;
+    auto const& rules = get_tzdb().rules;
+    if (y == r->ending_year())
+    {
+        if (r == &rules.back() || r->name() != r[1].name())
+            return {nullptr, year::max()};
+        ++r;
+        if (y == r->ending_year())
+            return {r, y};
+        return {r, r->starting_year()};
+    }
+    if (r == &rules.back() || r->name() != r[1].name() ||
+        r->ending_year() < r[1].ending_year())
+    {
+        while (r > &rules.front() && r->name() == r[-1].name() &&
+               r->starting_year() == r[-1].starting_year())
+            --r;
+        return {r, ++y};
+    }
+    ++r;
+    return {r, y};
+}
+
+static
+const Rule*
+find_first_std_rule(const std::pair<const Rule*, const Rule*>& eqr)
+{
+    auto r = eqr.first;
+    auto ry = r->starting_year();
+    while (r->save() != std::chrono::minutes{0})
+    {
+        std::tie(r, ry) = find_next_rule(eqr.first, eqr.second, r, ry);
+        if (r == nullptr)
+            throw std::runtime_error("Could not find standard offset in rule "
+                                     + eqr.first->name());
+    }
+    return r;
+}
+
+static
+std::pair<const Rule*, date::year>
+find_rule_for_zone(const std::pair<const Rule*, const Rule*>& eqr,
+                   const date::year& y, const std::chrono::seconds& offset,
+                   const MonthDayTime& mdt)
+{
+    assert(eqr.first != nullptr);
+    assert(eqr.second != nullptr);
+
+    using namespace std::chrono;
+    using namespace date;
+    auto r = eqr.first;
+    auto ry = r->starting_year();
+    auto prev_save = minutes{0};
+    auto prev_year = year::min();
+    const Rule* prev_rule = nullptr;
+    while (r != nullptr)
+    {
+        if (mdt.compare(y, r->mdt(), ry, offset, prev_save) <= 0)
+            break;
+        prev_rule = r;
+        prev_year = ry;
+        prev_save = prev_rule->save();
+        std::tie(r, ry) = find_next_rule(eqr.first, eqr.second, r, ry);
+    }
+    return {prev_rule, prev_year};
+}
+
+static
+std::pair<const Rule*, date::year>
+find_rule_for_zone(const std::pair<const Rule*, const Rule*>& eqr,
+                   const sys_seconds& tp_utc,
+                   const local_seconds& tp_std,
+                   const local_seconds& tp_loc)
+{
+    using namespace std::chrono;
+    using namespace date;
+    auto r = eqr.first;
+    auto ry = r->starting_year();
+    auto prev_save = minutes{0};
+    auto prev_year = year::min();
+    const Rule* prev_rule = nullptr;
+    while (r != nullptr)
+    {
+        bool found = false;
+        switch (r->mdt().zone())
+        {
+        case tz::utc:
+            found = tp_utc < r->mdt().to_time_point(ry);
+            break;
+        case tz::standard:
+            found = sys_seconds{tp_std.time_since_epoch()} < r->mdt().to_time_point(ry);
+            break;
+        case tz::local:
+            found = sys_seconds{tp_loc.time_since_epoch()} < r->mdt().to_time_point(ry);
+            break;
+        }
+        if (found)
+            break;
+        prev_rule = r;
+        prev_year = ry;
+        prev_save = prev_rule->save();
+        std::tie(r, ry) = find_next_rule(eqr.first, eqr.second, r, ry);
+    }
+    return {prev_rule, prev_year};
+}
+
+static
+sys_info
+find_rule(const std::pair<const Rule*, date::year>& first_rule,
+          const std::pair<const Rule*, date::year>& last_rule,
+          const date::year& y, const std::chrono::seconds& offset,
+          const MonthDayTime& mdt, const std::chrono::minutes& initial_save,
+          const std::string& initial_abbrev)
+{
+    using namespace std::chrono;
+    using namespace date;
+    auto r = first_rule.first;
+    auto ry = first_rule.second;
+    sys_info x{sys_days(year::min()/min_day), sys_days(year::max()/max_day),
+               seconds{0}, initial_save, initial_abbrev};
+    while (r != nullptr)
+    {
+        auto tr = r->mdt().to_sys(ry, offset, x.save);
+        auto tx = mdt.to_sys(y, offset, x.save);
+        // Find last rule where tx >= tr
+        if (tx <= tr || (r == last_rule.first && ry == last_rule.second))
+        {
+            if (tx < tr && r == first_rule.first && ry == first_rule.second)
+            {
+                x.end = r->mdt().to_sys(ry, offset, x.save);
+                break;
+            }
+            if (tx < tr)
+            {
+                std::tie(r, ry) = find_previous_rule(r, ry);  // can't return nullptr for r
+                assert(r != nullptr);
+            }
+            // r != nullptr && tx >= tr (if tr were to be recomputed)
+            auto prev_save = initial_save;
+            if (!(r == first_rule.first && ry == first_rule.second))
+                prev_save = find_previous_rule(r, ry).first->save();
+            x.begin = r->mdt().to_sys(ry, offset, prev_save);
+            x.save = r->save();
+            x.abbrev = r->abbrev();
+            if (!(r == last_rule.first && ry == last_rule.second))
+            {
+                std::tie(r, ry) = find_next_rule(r, ry);  // can't return nullptr for r
+                assert(r != nullptr);
+                x.end = r->mdt().to_sys(ry, offset, x.save);
+            }
+            else
+                x.end = sys_days(year::max()/max_day);
+            break;
+        }
+        x.save = r->save();
+        std::tie(r, ry) = find_next_rule(r, ry);  // Can't return nullptr for r
+        assert(r != nullptr);
+    }
+    return x;
+}
+
+// zonelet
+
+detail::zonelet::~zonelet()
+{
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    using minutes = std::chrono::minutes;
+    using string = std::string;
+    if (tag_ == has_save)
+        u.save_.~minutes();
+    else
+        u.rule_.~string();
+#endif
+}
+
+detail::zonelet::zonelet()
+{
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    ::new(&u.rule_) std::string();
+#endif
+}
+
+detail::zonelet::zonelet(const zonelet& i)
+    : gmtoff_(i.gmtoff_)
+    , tag_(i.tag_)
+    , format_(i.format_)
+    , until_year_(i.until_year_)
+    , until_date_(i.until_date_)
+    , until_utc_(i.until_utc_)
+    , until_std_(i.until_std_)
+    , until_loc_(i.until_loc_)
+    , initial_save_(i.initial_save_)
+    , initial_abbrev_(i.initial_abbrev_)
+    , first_rule_(i.first_rule_)
+    , last_rule_(i.last_rule_)
+{
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+    if (tag_ == has_save)
+        ::new(&u.save_) std::chrono::minutes(i.u.save_);
+    else
+        ::new(&u.rule_) std::string(i.u.rule_);
+#else
+    if (tag_ == has_save)
+        u.save_ = i.u.save_;
+    else
+        u.rule_ = i.u.rule_;
+#endif
+}
+
+#endif  // !USE_OS_TZDB
+
+// time_zone
+
+#if USE_OS_TZDB
+
+time_zone::time_zone(const std::string& s, detail::undocumented)
+    : name_(s)
+    , adjusted_(new std::once_flag{})
+{
+}
+
+enum class endian
+{
+    native = __BYTE_ORDER__,
+    little = __ORDER_LITTLE_ENDIAN__,
+    big    = __ORDER_BIG_ENDIAN__
+};
+
+static
+inline
+std::uint32_t
+reverse_bytes(std::uint32_t i)
+{
+    return
+        (i & 0xff000000u) >> 24 |
+        (i & 0x00ff0000u) >> 8 |
+        (i & 0x0000ff00u) << 8 |
+        (i & 0x000000ffu) << 24;
+}
+
+static
+inline
+std::uint64_t
+reverse_bytes(std::uint64_t i)
+{
+    return
+        (i & 0xff00000000000000ull) >> 56 |
+        (i & 0x00ff000000000000ull) >> 40 |
+        (i & 0x0000ff0000000000ull) >> 24 |
+        (i & 0x000000ff00000000ull) >> 8 |
+        (i & 0x00000000ff000000ull) << 8 |
+        (i & 0x0000000000ff0000ull) << 24 |
+        (i & 0x000000000000ff00ull) << 40 |
+        (i & 0x00000000000000ffull) << 56;
+}
+
+template <class T>
+static
+inline
+void
+maybe_reverse_bytes(T&, std::false_type)
+{
+}
+
+static
+inline
+void
+maybe_reverse_bytes(std::int32_t& t, std::true_type)
+{
+    t = static_cast<std::int32_t>(reverse_bytes(static_cast<std::uint32_t>(t)));
+}
+
+static
+inline
+void
+maybe_reverse_bytes(std::int64_t& t, std::true_type)
+{
+    t = static_cast<std::int64_t>(reverse_bytes(static_cast<std::uint64_t>(t)));
+}
+
+template <class T>
+static
+inline
+void
+maybe_reverse_bytes(T& t)
+{
+    maybe_reverse_bytes(t, std::integral_constant<bool,
+                                                  endian::native == endian::little>{});
+}
+
+static
+void
+load_header(std::istream& inf)
+{
+    // Read TZif
+    auto t = inf.get();
+    auto z = inf.get();
+    auto i = inf.get();
+    auto f = inf.get();
+#ifndef NDEBUG
+    assert(t == 'T');
+    assert(z == 'Z');
+    assert(i == 'i');
+    assert(f == 'f');
+#else
+    (void)t;
+    (void)z;
+    (void)i;
+    (void)f;
+#endif
+}
+
+static
+unsigned char
+load_version(std::istream& inf)
+{
+    // Read version
+    auto v = inf.get();
+    assert(v != EOF);
+    return static_cast<unsigned char>(v);
+}
+
+static
+void
+skip_reserve(std::istream& inf)
+{
+    inf.ignore(15);
+}
+
+static
+void
+load_counts(std::istream& inf,
+            std::int32_t& tzh_ttisgmtcnt, std::int32_t& tzh_ttisstdcnt,
+            std::int32_t& tzh_leapcnt,    std::int32_t& tzh_timecnt,
+            std::int32_t& tzh_typecnt,    std::int32_t& tzh_charcnt)
+{
+    // Read counts;
+    inf.read(reinterpret_cast<char*>(&tzh_ttisgmtcnt), 4);
+    maybe_reverse_bytes(tzh_ttisgmtcnt);
+    inf.read(reinterpret_cast<char*>(&tzh_ttisstdcnt), 4);
+    maybe_reverse_bytes(tzh_ttisstdcnt);
+    inf.read(reinterpret_cast<char*>(&tzh_leapcnt), 4);
+    maybe_reverse_bytes(tzh_leapcnt);
+    inf.read(reinterpret_cast<char*>(&tzh_timecnt), 4);
+    maybe_reverse_bytes(tzh_timecnt);
+    inf.read(reinterpret_cast<char*>(&tzh_typecnt), 4);
+    maybe_reverse_bytes(tzh_typecnt);
+    inf.read(reinterpret_cast<char*>(&tzh_charcnt), 4);
+    maybe_reverse_bytes(tzh_charcnt);
+}
+
+template <class TimeType>
+static
+std::vector<detail::transition>
+load_transitions(std::istream& inf, std::int32_t tzh_timecnt)
+{
+    // Read transitions
+    using namespace std::chrono;
+    std::vector<detail::transition> transitions;
+    transitions.reserve(static_cast<unsigned>(tzh_timecnt));
+    for (std::int32_t i = 0; i < tzh_timecnt; ++i)
+    {
+        TimeType t;
+        inf.read(reinterpret_cast<char*>(&t), sizeof(t));
+        maybe_reverse_bytes(t);
+        transitions.emplace_back(sys_seconds{seconds{t}});
+        if (transitions.back().timepoint < min_seconds)
+            transitions.back().timepoint = min_seconds;
+    }
+    return transitions;
+}
+
+static
+std::vector<std::uint8_t>
+load_indices(std::istream& inf, std::int32_t tzh_timecnt)
+{
+    // Read indices
+    std::vector<std::uint8_t> indices;
+    indices.reserve(static_cast<unsigned>(tzh_timecnt));
+    for (std::int32_t i = 0; i < tzh_timecnt; ++i)
+    {
+        std::uint8_t t;
+        inf.read(reinterpret_cast<char*>(&t), sizeof(t));
+        indices.emplace_back(t);
+    }
+    return indices;
+}
+
+static
+std::vector<ttinfo>
+load_ttinfo(std::istream& inf, std::int32_t tzh_typecnt)
+{
+    // Read ttinfo
+    std::vector<ttinfo> ttinfos;
+    ttinfos.reserve(static_cast<unsigned>(tzh_typecnt));
+    for (std::int32_t i = 0; i < tzh_typecnt; ++i)
+    {
+        ttinfo t;
+        inf.read(reinterpret_cast<char*>(&t), 6);
+        maybe_reverse_bytes(t.tt_gmtoff);
+        ttinfos.emplace_back(t);
+    }
+    return ttinfos;
+}
+
+static
+std::string
+load_abbreviations(std::istream& inf, std::int32_t tzh_charcnt)
+{
+    // Read abbreviations
+    std::string abbrev;
+    abbrev.resize(static_cast<unsigned>(tzh_charcnt), '\0');
+    inf.read(&abbrev[0], tzh_charcnt);
+    return abbrev;
+}
+
+#if !MISSING_LEAP_SECONDS
+
+template <class TimeType>
+static
+std::vector<leap_second>
+load_leaps(std::istream& inf, std::int32_t tzh_leapcnt)
+{
+    // Read tzh_leapcnt pairs
+    using namespace std::chrono;
+    std::vector<leap_second> leap_seconds;
+    leap_seconds.reserve(static_cast<std::size_t>(tzh_leapcnt));
+    for (std::int32_t i = 0; i < tzh_leapcnt; ++i)
+    {
+        TimeType     t0;
+        std::int32_t t1;
+        inf.read(reinterpret_cast<char*>(&t0), sizeof(t0));
+        inf.read(reinterpret_cast<char*>(&t1), sizeof(t1));
+        maybe_reverse_bytes(t0);
+        maybe_reverse_bytes(t1);
+        leap_seconds.emplace_back(sys_seconds{seconds{t0 - (t1-1)}},
+                                  detail::undocumented{});
+    }
+    return leap_seconds;
+}
+
+template <class TimeType>
+static
+std::vector<leap_second>
+load_leap_data(std::istream& inf,
+               std::int32_t tzh_leapcnt, std::int32_t tzh_timecnt,
+               std::int32_t tzh_typecnt, std::int32_t tzh_charcnt)
+{
+    inf.ignore(tzh_timecnt*static_cast<std::int32_t>(sizeof(TimeType)) + tzh_timecnt +
+               tzh_typecnt*6 + tzh_charcnt);
+    return load_leaps<TimeType>(inf, tzh_leapcnt);
+}
+
+static
+std::vector<leap_second>
+load_just_leaps(std::istream& inf)
+{
+    // Read tzh_leapcnt pairs
+    using namespace std::chrono;
+    load_header(inf);
+    auto v = load_version(inf);
+    std::int32_t tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+                 tzh_timecnt,    tzh_typecnt,    tzh_charcnt;
+    skip_reserve(inf);
+    load_counts(inf, tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+                     tzh_timecnt,    tzh_typecnt,    tzh_charcnt);
+    if (v == 0)
+        return load_leap_data<int32_t>(inf, tzh_leapcnt, tzh_timecnt, tzh_typecnt,
+                                       tzh_charcnt);
+#if !defined(NDEBUG)
+    inf.ignore((4+1)*tzh_timecnt + 6*tzh_typecnt + tzh_charcnt + 8*tzh_leapcnt +
+               tzh_ttisstdcnt + tzh_ttisgmtcnt);
+    load_header(inf);
+    auto v2 = load_version(inf);
+    assert(v == v2);
+    skip_reserve(inf);
+#else  // defined(NDEBUG)
+    inf.ignore((4+1)*tzh_timecnt + 6*tzh_typecnt + tzh_charcnt + 8*tzh_leapcnt +
+               tzh_ttisstdcnt + tzh_ttisgmtcnt + (4+1+15));
+#endif  // defined(NDEBUG)
+    load_counts(inf, tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+                     tzh_timecnt,    tzh_typecnt,    tzh_charcnt);
+    return load_leap_data<int64_t>(inf, tzh_leapcnt, tzh_timecnt, tzh_typecnt,
+                                   tzh_charcnt);
+}
+
+#endif  // !MISSING_LEAP_SECONDS
+
+template <class TimeType>
+void
+time_zone::load_data(std::istream& inf,
+                     std::int32_t tzh_leapcnt, std::int32_t tzh_timecnt,
+                     std::int32_t tzh_typecnt, std::int32_t tzh_charcnt)
+{
+    using namespace std::chrono;
+    transitions_ = load_transitions<TimeType>(inf, tzh_timecnt);
+    auto indices = load_indices(inf, tzh_timecnt);
+    auto infos = load_ttinfo(inf, tzh_typecnt);
+    auto abbrev = load_abbreviations(inf, tzh_charcnt);
+#if !MISSING_LEAP_SECONDS
+    auto& leap_seconds = get_tzdb_list().front().leap_seconds;
+    if (leap_seconds.empty() && tzh_leapcnt > 0)
+        leap_seconds = load_leaps<TimeType>(inf, tzh_leapcnt);
+#endif
+    ttinfos_.reserve(infos.size());
+    for (auto& info : infos)
+    {
+        ttinfos_.push_back({seconds{info.tt_gmtoff},
+                            abbrev.c_str() + info.tt_abbrind,
+                            info.tt_isdst != 0});
+    }
+    auto i = 0u;
+    if (transitions_.empty() || transitions_.front().timepoint != min_seconds)
+    {
+        transitions_.emplace(transitions_.begin(), min_seconds);
+        auto tf = std::find_if(ttinfos_.begin(), ttinfos_.end(),
+                               [](const expanded_ttinfo& ti)
+                                   {return ti.is_dst == 0;});
+        if (tf == ttinfos_.end())
+            tf = ttinfos_.begin();
+        transitions_[i].info = &*tf;
+        ++i;
+    }
+    for (auto j = 0u; i < transitions_.size(); ++i, ++j)
+        transitions_[i].info = ttinfos_.data() + indices[j];
+}
+
+void
+time_zone::init_impl()
+{
+    using namespace std;
+    using namespace std::chrono;
+    auto name = get_tz_dir() + ('/' + name_);
+    std::ifstream inf(name);
+    if (!inf.is_open())
+        throw std::runtime_error{"Unable to open " + name};
+    inf.exceptions(std::ios::failbit | std::ios::badbit);
+    load_header(inf);
+    auto v = load_version(inf);
+    std::int32_t tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+                 tzh_timecnt,    tzh_typecnt,    tzh_charcnt;
+    skip_reserve(inf);
+    load_counts(inf, tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+                     tzh_timecnt,    tzh_typecnt,    tzh_charcnt);
+    if (v == 0)
+    {
+        load_data<int32_t>(inf, tzh_leapcnt, tzh_timecnt, tzh_typecnt, tzh_charcnt);
+    }
+    else
+    {
+#if !defined(NDEBUG)
+        inf.ignore((4+1)*tzh_timecnt + 6*tzh_typecnt + tzh_charcnt + 8*tzh_leapcnt +
+                   tzh_ttisstdcnt + tzh_ttisgmtcnt);
+        load_header(inf);
+        auto v2 = load_version(inf);
+        assert(v == v2);
+        skip_reserve(inf);
+#else  // defined(NDEBUG)
+        inf.ignore((4+1)*tzh_timecnt + 6*tzh_typecnt + tzh_charcnt + 8*tzh_leapcnt +
+                   tzh_ttisstdcnt + tzh_ttisgmtcnt + (4+1+15));
+#endif  // defined(NDEBUG)
+        load_counts(inf, tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt,
+                         tzh_timecnt,    tzh_typecnt,    tzh_charcnt);
+        load_data<int64_t>(inf, tzh_leapcnt, tzh_timecnt, tzh_typecnt, tzh_charcnt);
+    }
+#if !MISSING_LEAP_SECONDS
+    if (tzh_leapcnt > 0)
+    {
+        auto& leap_seconds = get_tzdb_list().front().leap_seconds;
+        auto itr = leap_seconds.begin();
+        auto l = itr->date();
+        seconds leap_count{0};
+        for (auto t = std::upper_bound(transitions_.begin(), transitions_.end(), l,
+                                       [](const sys_seconds& x, const transition& ct)
+                                       {
+                                           return x < ct.timepoint;
+                                       });
+                  t != transitions_.end(); ++t)
+        {
+            while (t->timepoint >= l)
+            {
+                ++leap_count;
+                if (++itr == leap_seconds.end())
+                    l = sys_days(max_year/max_day);
+                else
+                    l = itr->date() + leap_count;
+            }
+            t->timepoint -= leap_count;
+        }
+    }
+#endif  // !MISSING_LEAP_SECONDS
+    auto b = transitions_.begin();
+    auto i = transitions_.end();
+    if (i != b)
+    {
+        for (--i; i != b; --i)
+        {
+            if (i->info->offset == i[-1].info->offset &&
+                i->info->abbrev == i[-1].info->abbrev &&
+                i->info->is_dst == i[-1].info->is_dst)
+                i = transitions_.erase(i);
+        }
+    }
+}
+
+void
+time_zone::init() const
+{
+    std::call_once(*adjusted_, [this]() {const_cast<time_zone*>(this)->init_impl();});
+}
+
+sys_info
+time_zone::load_sys_info(std::vector<detail::transition>::const_iterator i) const
+{
+    using namespace std::chrono;
+    assert(!transitions_.empty());
+    assert(i != transitions_.begin());
+    sys_info r;
+    r.begin = i[-1].timepoint;
+    r.end = i != transitions_.end() ? i->timepoint :
+                                      sys_seconds(sys_days(year::max()/max_day));
+    r.offset = i[-1].info->offset;
+    r.save = i[-1].info->is_dst ? minutes{1} : minutes{0};
+    r.abbrev = i[-1].info->abbrev;
+    return r;
+}
+
+sys_info
+time_zone::get_info_impl(sys_seconds tp) const
+{
+    using namespace std;
+    init();
+    return load_sys_info(upper_bound(transitions_.begin(), transitions_.end(), tp,
+                                     [](const sys_seconds& x, const transition& t)
+                                     {
+                                         return x < t.timepoint;
+                                     }));
+}
+
+local_info
+time_zone::get_info_impl(local_seconds tp) const
+{
+    using namespace std::chrono;
+    init();
+    local_info i;
+    i.result = local_info::unique;
+    auto tr = upper_bound(transitions_.begin(), transitions_.end(), tp,
+                          [](const local_seconds& x, const transition& t)
+                          {
+                              return sys_seconds{x.time_since_epoch()} -
+                                                         t.info->offset < t.timepoint;
+                          });
+    i.first = load_sys_info(tr);
+    auto tps = sys_seconds{(tp - i.first.offset).time_since_epoch()};
+    if (tps < i.first.begin + days{1} && tr != transitions_.begin())
+    {
+        i.second = load_sys_info(--tr);
+        tps = sys_seconds{(tp - i.second.offset).time_since_epoch()};
+        if (tps < i.second.end)
+        {
+           i.result = local_info::ambiguous;
+           std::swap(i.first, i.second);
+        }
+        else
+        {
+            i.second = {};
+        }
+    }
+    else if (tps >= i.first.end && tr != transitions_.end())
+    {
+        i.second = load_sys_info(++tr);
+        tps = sys_seconds{(tp - i.second.offset).time_since_epoch()};
+        if (tps < i.second.begin)
+            i.result = local_info::nonexistent;
+        else
+            i.second = {};
+    }
+    return i;
+}
+
+std::ostream&
+operator<<(std::ostream& os, const time_zone& z)
+{
+    using namespace std::chrono;
+    z.init();
+    os << z.name_ << '\n';
+    os << "Initially:           ";
+    auto const& t = z.transitions_.front();
+    if (t.info->offset >= seconds{0})
+        os << '+';
+    os << make_time(t.info->offset);
+    if (t.info->is_dst > 0)
+        os << " daylight ";
+    else
+        os << " standard ";
+    os << t.info->abbrev << '\n';
+    for (auto i = std::next(z.transitions_.cbegin()); i < z.transitions_.cend(); ++i)
+        os << *i << '\n';
+    return os;
+}
+
+#if !MISSING_LEAP_SECONDS
+
+leap_second::leap_second(const sys_seconds& s, detail::undocumented)
+    : date_(s)
+{
+}
+
+#endif  // !MISSING_LEAP_SECONDS
+
+#else  // !USE_OS_TZDB
+
+time_zone::time_zone(const std::string& s, detail::undocumented)
+    : adjusted_(new std::once_flag{})
+{
+    try
+    {
+        using namespace date;
+        std::istringstream in(s);
+        in.exceptions(std::ios::failbit | std::ios::badbit);
+        std::string word;
+        in >> word >> name_;
+        parse_info(in);
+    }
+    catch (...)
+    {
+        std::cerr << s << '\n';
+        std::cerr << *this << '\n';
+        zonelets_.pop_back();
+        throw;
+    }
+}
+
+sys_info
+time_zone::get_info_impl(sys_seconds tp) const
+{
+    return get_info_impl(tp, static_cast<int>(tz::utc));
+}
+
+local_info
+time_zone::get_info_impl(local_seconds tp) const
+{
+    using namespace std::chrono;
+    local_info i{};
+    i.first = get_info_impl(sys_seconds{tp.time_since_epoch()}, static_cast<int>(tz::local));
+    auto tps = sys_seconds{(tp - i.first.offset).time_since_epoch()};
+    if (tps < i.first.begin)
+    {
+        i.second = std::move(i.first);
+        i.first = get_info_impl(i.second.begin - seconds{1}, static_cast<int>(tz::utc));
+        i.result = local_info::nonexistent;
+    }
+    else if (i.first.end - tps <= days{1})
+    {
+        i.second = get_info_impl(i.first.end, static_cast<int>(tz::utc));
+        tps = sys_seconds{(tp - i.second.offset).time_since_epoch()};
+        if (tps >= i.second.begin)
+            i.result = local_info::ambiguous;
+        else
+            i.second = {};
+    }
+    return i;
+}
+
+void
+time_zone::add(const std::string& s)
+{
+    try
+    {
+        std::istringstream in(s);
+        in.exceptions(std::ios::failbit | std::ios::badbit);
+        ws(in);
+        if (!in.eof() && in.peek() != '#')
+            parse_info(in);
+    }
+    catch (...)
+    {
+        std::cerr << s << '\n';
+        std::cerr << *this << '\n';
+        zonelets_.pop_back();
+        throw;
+    }
+}
+
+void
+time_zone::parse_info(std::istream& in)
+{
+    using namespace date;
+    using namespace std::chrono;
+    zonelets_.emplace_back();
+    auto& zonelet = zonelets_.back();
+    zonelet.gmtoff_ = parse_signed_time(in);
+    in >> zonelet.u.rule_;
+    if (zonelet.u.rule_ == "-")
+        zonelet.u.rule_.clear();
+    in >> zonelet.format_;
+    if (!in.eof())
+        ws(in);
+    if (in.eof() || in.peek() == '#')
+    {
+        zonelet.until_year_ = year::max();
+        zonelet.until_date_ = MonthDayTime(max_day, tz::utc);
+    }
+    else
+    {
+        int y;
+        in >> y;
+        zonelet.until_year_ = year{y};
+        in >> zonelet.until_date_;
+        zonelet.until_date_.canonicalize(zonelet.until_year_);
+    }
+    if ((zonelet.until_year_ < min_year) ||
+            (zonelets_.size() > 1 && zonelets_.end()[-2].until_year_ > max_year))
+        zonelets_.pop_back();
+}
+
+void
+time_zone::adjust_infos(const std::vector<Rule>& rules)
+{
+    using namespace std::chrono;
+    using namespace date;
+    const zonelet* prev_zonelet = nullptr;
+    for (auto& z : zonelets_)
+    {
+        std::pair<const Rule*, const Rule*> eqr{};
+        std::istringstream in;
+        in.exceptions(std::ios::failbit | std::ios::badbit);
+        // Classify info as rule-based, has save, or neither
+        if (!z.u.rule_.empty())
+        {
+            // Find out if this zonelet has a rule or a save
+            eqr = std::equal_range(rules.data(), rules.data() + rules.size(), z.u.rule_);
+            if (eqr.first == eqr.second)
+            {
+                // The rule doesn't exist.  Assume this is a save
+                try
+                {
+                    using namespace std::chrono;
+                    using string = std::string;
+                    in.str(z.u.rule_);
+                    auto tmp = duration_cast<minutes>(parse_signed_time(in));
+#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
+                    z.u.rule_.~string();
+                    z.tag_ = zonelet::has_save;
+                    ::new(&z.u.save_) minutes(tmp);
+#else
+                    z.u.rule_.clear();
+                    z.tag_ = zonelet::has_save;
+                    z.u.save_ = tmp;
+#endif
+                }
+                catch (...)
+                {
+                    std::cerr << name_ << " : " << z.u.rule_ << '\n';
+                    throw;
+                }
+            }
+        }
+        else
+        {
+            // This zone::zonelet has no rule and no save
+            z.tag_ = zonelet::is_empty;
+        }
+
+        minutes final_save{0};
+        if (z.tag_ == zonelet::has_save)
+        {
+            final_save = z.u.save_;
+        }
+        else if (z.tag_ == zonelet::has_rule)
+        {
+            z.last_rule_ = find_rule_for_zone(eqr, z.until_year_, z.gmtoff_,
+                                              z.until_date_);
+            if (z.last_rule_.first != nullptr)
+                final_save = z.last_rule_.first->save();
+        }
+        z.until_utc_ = z.until_date_.to_sys(z.until_year_, z.gmtoff_, final_save);
+        z.until_std_ = local_seconds{z.until_utc_.time_since_epoch()} + z.gmtoff_;
+        z.until_loc_ = z.until_std_ + final_save;
+
+        if (z.tag_ == zonelet::has_rule)
+        {
+            if (prev_zonelet != nullptr)
+            {
+                z.first_rule_ = find_rule_for_zone(eqr, prev_zonelet->until_utc_,
+                                                        prev_zonelet->until_std_,
+                                                        prev_zonelet->until_loc_);
+                if (z.first_rule_.first != nullptr)
+                {
+                    z.initial_save_ = z.first_rule_.first->save();
+                    z.initial_abbrev_ = z.first_rule_.first->abbrev();
+                    if (z.first_rule_ != z.last_rule_)
+                    {
+                        z.first_rule_ = find_next_rule(eqr.first, eqr.second,
+                                                       z.first_rule_.first,
+                                                       z.first_rule_.second);
+                    }
+                    else
+                    {
+                        z.first_rule_ = std::make_pair(nullptr, year::min());
+                        z.last_rule_ = std::make_pair(nullptr, year::max());
+                    }
+                }
+            }
+            if (z.first_rule_.first == nullptr && z.last_rule_.first != nullptr)
+            {
+                z.first_rule_ = std::make_pair(eqr.first, eqr.first->starting_year());
+                z.initial_abbrev_ = find_first_std_rule(eqr)->abbrev();
+            }
+        }
+
+#ifndef NDEBUG
+        if (z.first_rule_.first == nullptr)
+        {
+            assert(z.first_rule_.second == year::min());
+            assert(z.last_rule_.first == nullptr);
+            assert(z.last_rule_.second == year::max());
+        }
+        else
+        {
+            assert(z.last_rule_.first != nullptr);
+        }
+#endif
+        prev_zonelet = &z;
+    }
+}
+
+static
+std::string
+format_abbrev(std::string format, const std::string& variable, std::chrono::seconds off,
+                                                               std::chrono::minutes save)
+{
+    using namespace std::chrono;
+    auto k = format.find("%s");
+    if (k != std::string::npos)
+    {
+        format.replace(k, 2, variable);
+    }
+    else
+    {
+        k = format.find('/');
+        if (k != std::string::npos)
+        {
+            if (save == minutes{0})
+                format.erase(k);
+            else
+                format.erase(0, k+1);
+        }
+        else
+        {
+            k = format.find("%z");
+            if (k != std::string::npos)
+            {
+                std::string temp;
+                if (off < seconds{0})
+                {
+                    temp = '-';
+                    off = -off;
+                }
+                else
+                    temp = '+';
+                auto h = date::floor<hours>(off);
+                off -= h;
+                if (h < hours{10})
+                    temp += '0';
+                temp += std::to_string(h.count());
+                if (off > seconds{0})
+                {
+                    auto m = date::floor<minutes>(off);
+                    off -= m;
+                    if (m < minutes{10})
+                        temp += '0';
+                    temp += std::to_string(m.count());
+                    if (off > seconds{0})
+                    {
+                        if (off < seconds{10})
+                            temp += '0';
+                        temp += std::to_string(off.count());
+                    }
+                }
+                format.replace(k, 2, temp);
+            }
+        }
+    }
+    return format;
+}
+
+sys_info
+time_zone::get_info_impl(sys_seconds tp, int tz_int) const
+{
+    using namespace std::chrono;
+    using namespace date;
+    tz timezone = static_cast<tz>(tz_int);
+    assert(timezone != tz::standard);
+    auto y = year_month_day(floor<days>(tp)).year();
+    if (y < min_year || y > max_year)
+        throw std::runtime_error("The year " + std::to_string(static_cast<int>(y)) +
+            " is out of range:[" + std::to_string(static_cast<int>(min_year)) + ", "
+                                 + std::to_string(static_cast<int>(max_year)) + "]");
+    std::call_once(*adjusted_,
+                   [this]()
+                   {
+                       const_cast<time_zone*>(this)->adjust_infos(get_tzdb().rules);
+                   });
+    auto i = std::upper_bound(zonelets_.begin(), zonelets_.end(), tp,
+        [timezone](sys_seconds t, const zonelet& zl)
+        {
+            return timezone == tz::utc ? t < zl.until_utc_ :
+                                         t < sys_seconds{zl.until_loc_.time_since_epoch()};
+        });
+
+    sys_info r{};
+    if (i != zonelets_.end())
+    {
+        if (i->tag_ == zonelet::has_save)
+        {
+            if (i != zonelets_.begin())
+                r.begin = i[-1].until_utc_;
+            else
+                r.begin = sys_days(year::min()/min_day);
+            r.end = i->until_utc_;
+            r.offset = i->gmtoff_ + i->u.save_;
+            r.save = i->u.save_;
+        }
+        else if (i->u.rule_.empty())
+        {
+            if (i != zonelets_.begin())
+                r.begin = i[-1].until_utc_;
+            else
+                r.begin = sys_days(year::min()/min_day);
+            r.end = i->until_utc_;
+            r.offset = i->gmtoff_;
+        }
+        else
+        {
+            r = find_rule(i->first_rule_, i->last_rule_, y, i->gmtoff_,
+                          MonthDayTime(local_seconds{tp.time_since_epoch()}, timezone),
+                          i->initial_save_, i->initial_abbrev_);
+            r.offset = i->gmtoff_ + r.save;
+            if (i != zonelets_.begin() && r.begin < i[-1].until_utc_)
+                r.begin = i[-1].until_utc_;
+            if (r.end > i->until_utc_)
+                r.end = i->until_utc_;
+        }
+        r.abbrev = format_abbrev(i->format_, r.abbrev, r.offset, r.save);
+        assert(r.begin < r.end);
+    }
+    return r;
+}
+
+std::ostream&
+operator<<(std::ostream& os, const time_zone& z)
+{
+    using namespace date;
+    using namespace std::chrono;
+    detail::save_ostream<char> _(os);
+    os.fill(' ');
+    os.flags(std::ios::dec | std::ios::left);
+    std::call_once(*z.adjusted_,
+                   [&z]()
+                   {
+                       const_cast<time_zone&>(z).adjust_infos(get_tzdb().rules);
+                   });
+    os.width(35);
+    os << z.name_;
+    std::string indent;
+    for (auto const& s : z.zonelets_)
+    {
+        os << indent;
+        if (s.gmtoff_ >= seconds{0})
+            os << ' ';
+        os << make_time(s.gmtoff_) << "   ";
+        os.width(15);
+        if (s.tag_ != zonelet::has_save)
+            os << s.u.rule_;
+        else
+        {
+            std::ostringstream tmp;
+            tmp << make_time(s.u.save_);
+            os <<  tmp.str();
+        }
+        os.width(8);
+        os << s.format_ << "   ";
+        os << s.until_year_ << ' ' << s.until_date_;
+        os << "   " << s.until_utc_ << " UTC";
+        os << "   " << s.until_std_ << " STD";
+        os << "   " << s.until_loc_;
+        os << "   " << make_time(s.initial_save_);
+        os << "   " << s.initial_abbrev_;
+        if (s.first_rule_.first != nullptr)
+            os << "   {" << *s.first_rule_.first << ", " << s.first_rule_.second << '}';
+        else
+            os << "   {" << "nullptr" << ", " << s.first_rule_.second << '}';
+        if (s.last_rule_.first != nullptr)
+            os << "   {" << *s.last_rule_.first << ", " << s.last_rule_.second << '}';
+        else
+            os << "   {" << "nullptr" << ", " << s.last_rule_.second << '}';
+        os << '\n';
+        if (indent.empty())
+            indent = std::string(35, ' ');
+    }
+    return os;
+}
+
+#endif  // !USE_OS_TZDB
+
+#if !MISSING_LEAP_SECONDS
+
+std::ostream&
+operator<<(std::ostream& os, const leap_second& x)
+{
+    using namespace date;
+    return os << x.date_ << "  +";
+}
+
+#endif  // !MISSING_LEAP_SECONDS
+
+#if USE_OS_TZDB
+
+# ifdef __APPLE__
+static
+std::string
+get_version()
+{
+    using namespace std;
+    auto path = get_tz_dir() + string("/+VERSION");
+    ifstream in{path};
+    string version;
+    in >> version;
+    if (in.fail())
+        throw std::runtime_error("Unable to get Timezone database version from " + path);
+    return version;
+}
+# endif
+
+static
+std::unique_ptr<tzdb>
+init_tzdb()
+{
+    std::unique_ptr<tzdb> db(new tzdb);
+
+    //Iterate through folders
+    std::queue<std::string> subfolders;
+    subfolders.emplace(get_tz_dir());
+    struct dirent* d;
+    struct stat s;
+    while (!subfolders.empty())
+    {
+        auto dirname = std::move(subfolders.front());
+        subfolders.pop();
+        auto dir = opendir(dirname.c_str());
+        if (!dir)
+            continue;
+        while ((d = readdir(dir)) != nullptr)
+        {
+            // Ignore these files:
+            if (d->d_name[0]                      == '.'    || // curdir, prevdir, hidden
+                memcmp(d->d_name, "posix", 5)     == 0      || // starts with posix
+                strcmp(d->d_name, "Factory")      == 0      ||
+                strcmp(d->d_name, "iso3166.tab")  == 0      ||
+                strcmp(d->d_name, "right")        == 0      ||
+                strcmp(d->d_name, "+VERSION")     == 0      ||
+                strcmp(d->d_name, "zone.tab")     == 0      ||
+                strcmp(d->d_name, "zone1970.tab") == 0      ||
+                strcmp(d->d_name, "tzdata.zi")    == 0      ||
+                strcmp(d->d_name, "leapseconds")  == 0      ||
+                strcmp(d->d_name, "leap-seconds.list") == 0   )
+                continue;
+            auto subname = dirname + folder_delimiter + d->d_name;
+            if(stat(subname.c_str(), &s) == 0)
+            {
+                if(S_ISDIR(s.st_mode))
+                {
+                    if(!S_ISLNK(s.st_mode))
+                    {
+                        subfolders.push(subname);
+                    }
+                }
+                else
+                {
+                    db->zones.emplace_back(subname.substr(get_tz_dir().size()+1),
+                                           detail::undocumented{});
+                }
+            }
+        }
+        closedir(dir);
+    }
+    db->zones.shrink_to_fit();
+    std::sort(db->zones.begin(), db->zones.end());
+#  if !MISSING_LEAP_SECONDS
+    std::ifstream in(get_tz_dir() + std::string(1, folder_delimiter) + "right/UTC",
+                     std::ios_base::binary);
+    if (in)
+    {
+        in.exceptions(std::ios::failbit | std::ios::badbit);
+        db->leap_seconds = load_just_leaps(in);
+    }
+    else
+    {
+        in.clear();
+        in.open(get_tz_dir() + std::string(1, folder_delimiter) +
+                "UTC", std::ios_base::binary);
+        if (!in)
+            throw std::runtime_error("Unable to extract leap second information");
+        in.exceptions(std::ios::failbit | std::ios::badbit);
+        db->leap_seconds = load_just_leaps(in);
+    }
+#  endif  // !MISSING_LEAP_SECONDS
+#  ifdef __APPLE__
+    db->version = get_version();
+#  endif
+    return db;
+}
+
+#else  // !USE_OS_TZDB
+
+// time_zone_link
+
+time_zone_link::time_zone_link(const std::string& s)
+{
+    using namespace date;
+    std::istringstream in(s);
+    in.exceptions(std::ios::failbit | std::ios::badbit);
+    std::string word;
+    in >> word >> target_ >> name_;
+}
+
+std::ostream&
+operator<<(std::ostream& os, const time_zone_link& x)
+{
+    using namespace date;
+    detail::save_ostream<char> _(os);
+    os.fill(' ');
+    os.flags(std::ios::dec | std::ios::left);
+    os.width(35);
+    return os << x.name_ << " --> " << x.target_;
+}
+
+// leap_second
+
+leap_second::leap_second(const std::string& s, detail::undocumented)
+{
+    using namespace date;
+    std::istringstream in(s);
+    in.exceptions(std::ios::failbit | std::ios::badbit);
+    std::string word;
+    int y;
+    MonthDayTime date;
+    in >> word >> y >> date;
+    date_ = date.to_time_point(year(y));
+}
+
+static
+bool
+file_exists(const std::string& filename)
+{
+#ifdef _WIN32
+    return ::_access(filename.c_str(), 0) == 0;
+#else
+    return ::access(filename.c_str(), F_OK) == 0;
+#endif
+}
+
+#if HAS_REMOTE_API
+
+// CURL tools
+
+static
+int
+curl_global()
+{
+    if (::curl_global_init(CURL_GLOBAL_DEFAULT) != 0)
+        throw std::runtime_error("CURL global initialization failed");
+    return 0;
+}
+
+namespace
+{
+
+struct curl_deleter
+{
+    void operator()(CURL* p) const
+    {
+        ::curl_easy_cleanup(p);
+    }
+};
+
+}  // unnamed namespace
+
+static
+std::unique_ptr<CURL, curl_deleter>
+curl_init()
+{
+    static const auto curl_is_now_initiailized = curl_global();
+    (void)curl_is_now_initiailized;
+    return std::unique_ptr<CURL, curl_deleter>{::curl_easy_init()};
+}
+
+static
+bool
+download_to_string(const std::string& url, std::string& str)
+{
+    str.clear();
+    auto curl = curl_init();
+    if (!curl)
+        return false;
+    std::string version;
+    curl_easy_setopt(curl.get(), CURLOPT_USERAGENT, "curl");
+    curl_easy_setopt(curl.get(), CURLOPT_URL, url.c_str());
+    curl_write_callback write_cb = [](char* contents, std::size_t size, std::size_t nmemb,
+                                      void* userp) -> std::size_t
+    {
+        auto& userstr = *static_cast<std::string*>(userp);
+        auto realsize = size * nmemb;
+        userstr.append(contents, realsize);
+        return realsize;
+    };
+    curl_easy_setopt(curl.get(), CURLOPT_WRITEFUNCTION, write_cb);
+    curl_easy_setopt(curl.get(), CURLOPT_WRITEDATA, &str);
+    curl_easy_setopt(curl.get(), CURLOPT_SSL_VERIFYPEER, false);
+    auto res = curl_easy_perform(curl.get());
+    return (res == CURLE_OK);
+}
+
+namespace
+{
+    enum class download_file_options { binary, text };
+}
+
+static
+bool
+download_to_file(const std::string& url, const std::string& local_filename,
+                 download_file_options opts, char* error_buffer)
+{
+    auto curl = curl_init();
+    if (!curl)
+        return false;
+    curl_easy_setopt(curl.get(), CURLOPT_URL, url.c_str());
+    curl_easy_setopt(curl.get(), CURLOPT_SSL_VERIFYPEER, false);
+    if (error_buffer)
+       curl_easy_setopt(curl.get(), CURLOPT_ERRORBUFFER, error_buffer);
+    curl_write_callback write_cb = [](char* contents, std::size_t size, std::size_t nmemb,
+                                      void* userp) -> std::size_t
+    {
+        auto& of = *static_cast<std::ofstream*>(userp);
+        auto realsize = size * nmemb;
+        of.write(contents, static_cast<std::streamsize>(realsize));
+        return realsize;
+    };
+    curl_easy_setopt(curl.get(), CURLOPT_WRITEFUNCTION, write_cb);
+    decltype(curl_easy_perform(curl.get())) res;
+    {
+        std::ofstream of(local_filename,
+                         opts == download_file_options::binary ?
+                             std::ofstream::out | std::ofstream::binary :
+                             std::ofstream::out);
+        of.exceptions(std::ios::badbit);
+        curl_easy_setopt(curl.get(), CURLOPT_WRITEDATA, &of);
+        res = curl_easy_perform(curl.get());
+    }
+    return res == CURLE_OK;
+}
+
+std::string
+remote_version()
+{
+    std::string version;
+    std::string str;
+    if (download_to_string("https://www.iana.org/time-zones", str))
+    {
+        CONSTDATA char db[] = "/time-zones/releases/tzdata";
+        CONSTDATA auto db_size = sizeof(db) - 1;
+        auto p = str.find(db, 0, db_size);
+        const int ver_str_len = 5;
+        if (p != std::string::npos && p + (db_size + ver_str_len) <= str.size())
+            version = str.substr(p + db_size, ver_str_len);
+    }
+    return version;
+}
+
+
+// TODO! Using system() create a process and a console window.
+// This is useful to see what errors may occur but is slow and distracting.
+// Consider implementing this functionality more directly, such as
+// using _mkdir and CreateProcess etc.
+// But use the current means now as matches Unix implementations and while
+// in proof of concept / testing phase.
+// TODO! Use <filesystem> eventually.
+static
+bool
+remove_folder_and_subfolders(const std::string& folder)
+{
+#  ifdef _WIN32
+#    if USE_SHELL_API
+    // Delete the folder contents by deleting the folder.
+    std::string cmd = "rd /s /q \"";
+    cmd += folder;
+    cmd += '\"';
+    return std::system(cmd.c_str()) == EXIT_SUCCESS;
+#    else  // !USE_SHELL_API
+    // Create a buffer containing the path to delete. It must be terminated
+    // by two nuls. Who designs these API's...
+    std::vector<char> from;
+    from.assign(folder.begin(), folder.end());
+    from.push_back('\0');
+    from.push_back('\0');
+    SHFILEOPSTRUCT fo{}; // Zero initialize.
+    fo.wFunc = FO_DELETE;
+    fo.pFrom = from.data();
+    fo.fFlags = FOF_NO_UI;
+    int ret = SHFileOperation(&fo);
+    if (ret == 0 && !fo.fAnyOperationsAborted)
+        return true;
+    return false;
+#    endif  // !USE_SHELL_API
+#  else   // !_WIN32
+#    if USE_SHELL_API
+    return std::system(("rm -R " + folder).c_str()) == EXIT_SUCCESS;
+#    else // !USE_SHELL_API
+    struct dir_deleter {
+        dir_deleter() {}
+        void operator()(DIR* d) const
+        {
+            if (d != nullptr)
+            {
+                int result = closedir(d);
+                assert(result == 0);
+            }
+        }
+    };
+    using closedir_ptr = std::unique_ptr<DIR, dir_deleter>;
+
+    std::string filename;
+    struct stat statbuf;
+    std::size_t folder_len = folder.length();
+    struct dirent* p = nullptr;
+
+    closedir_ptr d(opendir(folder.c_str()));
+    bool r = d.get() != nullptr;
+    while (r && (p=readdir(d.get())) != nullptr)
+    {
+        if (strcmp(p->d_name, ".") == 0 || strcmp(p->d_name, "..") == 0)
+           continue;
+
+        // + 2 for path delimiter and nul terminator.
+        std::size_t buf_len = folder_len + strlen(p->d_name) + 2;
+        filename.resize(buf_len);
+        std::size_t path_len = static_cast<std::size_t>(
+            snprintf(&filename[0], buf_len, "%s/%s", folder.c_str(), p->d_name));
+        assert(path_len == buf_len - 1);
+        filename.resize(path_len);
+
+        if (stat(filename.c_str(), &statbuf) == 0)
+            r = S_ISDIR(statbuf.st_mode)
+              ? remove_folder_and_subfolders(filename)
+              : unlink(filename.c_str()) == 0;
+    }
+    d.reset();
+
+    if (r)
+        r = rmdir(folder.c_str()) == 0;
+
+    return r;
+#    endif // !USE_SHELL_API
+#  endif  // !_WIN32
+}
+
+static
+bool
+make_directory(const std::string& folder)
+{
+#  ifdef _WIN32
+#    if USE_SHELL_API
+    // Re-create the folder.
+    std::string cmd = "mkdir \"";
+    cmd += folder;
+    cmd += '\"';
+    return std::system(cmd.c_str()) == EXIT_SUCCESS;
+#    else  // !USE_SHELL_API
+    return _mkdir(folder.c_str()) == 0;
+#    endif // !USE_SHELL_API
+#  else  // !_WIN32
+#    if USE_SHELL_API
+    return std::system(("mkdir -p " + folder).c_str()) == EXIT_SUCCESS;
+#    else  // !USE_SHELL_API
+    return mkdir(folder.c_str(), 0777) == 0;
+#    endif  // !USE_SHELL_API
+#  endif  // !_WIN32
+}
+
+static
+bool
+delete_file(const std::string& file)
+{
+#  ifdef _WIN32
+#    if USE_SHELL_API
+    std::string cmd = "del \"";
+    cmd += file;
+    cmd += '\"';
+    return std::system(cmd.c_str()) == 0;
+#    else  // !USE_SHELL_API
+    return _unlink(file.c_str()) == 0;
+#    endif // !USE_SHELL_API
+#  else  // !_WIN32
+#    if USE_SHELL_API
+    return std::system(("rm " + file).c_str()) == EXIT_SUCCESS;
+#    else // !USE_SHELL_API
+    return unlink(file.c_str()) == 0;
+#    endif // !USE_SHELL_API
+#  endif  // !_WIN32
+}
+
+#  ifdef _WIN32
+
+static
+bool
+move_file(const std::string& from, const std::string& to)
+{
+#    if USE_SHELL_API
+    std::string cmd = "move \"";
+    cmd += from;
+    cmd += "\" \"";
+    cmd += to;
+    cmd += '\"';
+    return std::system(cmd.c_str()) == EXIT_SUCCESS;
+#    else  // !USE_SHELL_API
+    return !!::MoveFile(from.c_str(), to.c_str());
+#    endif // !USE_SHELL_API
+}
+
+// Usually something like "c:\Program Files".
+static
+std::string
+get_program_folder()
+{
+    return get_known_folder(FOLDERID_ProgramFiles);
+}
+
+// Note folder can and usually does contain spaces.
+static
+std::string
+get_unzip_program()
+{
+    std::string path;
+
+    // 7-Zip appears to note its location in the registry.
+    // If that doesn't work, fall through and take a guess, but it will likely be wrong.
+    HKEY hKey = nullptr;
+    if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, "SOFTWARE\\7-Zip", 0, KEY_READ, &hKey) == ERROR_SUCCESS)
+    {
+        char value_buffer[MAX_PATH + 1]; // fyi 260 at time of writing.
+        // in/out parameter. Documentation say that size is a count of bytes not chars.
+        DWORD size = sizeof(value_buffer) - sizeof(value_buffer[0]);
+        DWORD tzi_type = REG_SZ;
+        // Testing shows Path key value is "C:\Program Files\7-Zip\" i.e. always with trailing \.
+        bool got_value = (RegQueryValueExA(hKey, "Path", nullptr, &tzi_type,
+            reinterpret_cast<LPBYTE>(value_buffer), &size) == ERROR_SUCCESS);
+        RegCloseKey(hKey); // Close now incase of throw later.
+        if (got_value)
+        {
+            // Function does not guarantee to null terminate.
+            value_buffer[size / sizeof(value_buffer[0])] = '\0';
+            path = value_buffer;
+            if (!path.empty())
+            {
+                path += "7z.exe";
+                return path;
+            }
+        }
+    }
+    path += get_program_folder();
+    path += folder_delimiter;
+    path += "7-Zip\\7z.exe";
+    return path;
+}
+
+#    if !USE_SHELL_API
+static
+int
+run_program(const std::string& command)
+{
+    STARTUPINFO si{};
+    si.cb = sizeof(si);
+    PROCESS_INFORMATION pi{};
+
+    // Allegedly CreateProcess overwrites the command line. Ugh.
+    std::string mutable_command(command);
+    if (CreateProcess(nullptr, &mutable_command[0],
+        nullptr, nullptr, FALSE, CREATE_NO_WINDOW, nullptr, nullptr, &si, &pi))
+    {
+        WaitForSingleObject(pi.hProcess, INFINITE);
+        DWORD exit_code;
+        bool got_exit_code = !!GetExitCodeProcess(pi.hProcess, &exit_code);
+        CloseHandle(pi.hProcess);
+        CloseHandle(pi.hThread);
+        // Not 100% sure about this still active thing is correct,
+        // but I'm going with it because I *think* WaitForSingleObject might
+        // return in some cases without INFINITE-ly waiting.
+        // But why/wouldn't GetExitCodeProcess return false in that case?
+        if (got_exit_code && exit_code != STILL_ACTIVE)
+            return static_cast<int>(exit_code);
+    }
+    return EXIT_FAILURE;
+}
+#    endif // !USE_SHELL_API
+
+static
+std::string
+get_download_tar_file(const std::string& version)
+{
+    auto file = get_install();
+    file += folder_delimiter;
+    file += "tzdata";
+    file += version;
+    file += ".tar";
+    return file;
+}
+
+static
+bool
+extract_gz_file(const std::string& version, const std::string& gz_file,
+                const std::string& dest_folder)
+{
+    auto unzip_prog = get_unzip_program();
+    bool unzip_result = false;
+    // Use the unzip program to extract the tar file from the archive.
+
+    // Aim to create a string like:
+    // "C:\Program Files\7-Zip\7z.exe" x "C:\Users\SomeUser\Downloads\tzdata2016d.tar.gz"
+    //     -o"C:\Users\SomeUser\Downloads\tzdata"
+    std::string cmd;
+    cmd = '\"';
+    cmd += unzip_prog;
+    cmd += "\" x \"";
+    cmd += gz_file;
+    cmd += "\" -o\"";
+    cmd += dest_folder;
+    cmd += '\"';
+
+#    if USE_SHELL_API
+    // When using shelling out with std::system() extra quotes are required around the
+    // whole command. It's weird but necessary it seems, see:
+    // http://stackoverflow.com/q/27975969/576911
+
+    cmd = "\"" + cmd + "\"";
+    if (std::system(cmd.c_str()) == EXIT_SUCCESS)
+        unzip_result = true;
+#    else  // !USE_SHELL_API
+    if (run_program(cmd) == EXIT_SUCCESS)
+        unzip_result = true;
+#    endif // !USE_SHELL_API
+    if (unzip_result)
+        delete_file(gz_file);
+
+    // Use the unzip program extract the data from the tar file that was
+    // just extracted from the archive.
+    auto tar_file = get_download_tar_file(version);
+    cmd = '\"';
+    cmd += unzip_prog;
+    cmd += "\" x \"";
+    cmd += tar_file;
+    cmd += "\" -o\"";
+    cmd += get_install();
+    cmd += '\"';
+#    if USE_SHELL_API
+    cmd = "\"" + cmd + "\"";
+    if (std::system(cmd.c_str()) == EXIT_SUCCESS)
+        unzip_result = true;
+#    else  // !USE_SHELL_API
+    if (run_program(cmd) == EXIT_SUCCESS)
+        unzip_result = true;
+#    endif // !USE_SHELL_API
+
+    if (unzip_result)
+        delete_file(tar_file);
+
+    return unzip_result;
+}
+
+static
+std::string
+get_download_mapping_file(const std::string& version)
+{
+    auto file = get_install() + version + "windowsZones.xml";
+    return file;
+}
+
+#  else  // !_WIN32
+
+#    if !USE_SHELL_API
+static
+int
+run_program(const char* prog, const char*const args[])
+{
+    pid_t pid = fork();
+    if (pid == -1) // Child failed to start.
+        return EXIT_FAILURE;
+
+    if (pid != 0)
+    {
+        // We are in the parent. Child started. Wait for it.
+        pid_t ret;
+        int status;
+        while ((ret = waitpid(pid, &status, 0)) == -1)
+        {
+            if (errno != EINTR)
+                break;
+        }
+        if (ret != -1)
+        {
+            if (WIFEXITED(status))
+                return WEXITSTATUS(status);
+        }
+        printf("Child issues!\n");
+
+        return EXIT_FAILURE; // Not sure what status of child is.
+    }
+    else // We are in the child process. Start the program the parent wants to run.
+    {
+
+        if (execv(prog, const_cast<char**>(args)) == -1) // Does not return.
+        {
+            perror("unreachable 0\n");
+            _Exit(127);
+        }
+        printf("unreachable 2\n");
+    }
+    printf("unreachable 2\n");
+    // Unreachable.
+    assert(false);
+    exit(EXIT_FAILURE);
+    return EXIT_FAILURE;
+}
+#    endif // !USE_SHELL_API
+
+static
+bool
+extract_gz_file(const std::string&, const std::string& gz_file, const std::string&)
+{
+#    if USE_SHELL_API
+    bool unzipped = std::system(("tar -xzf " + gz_file + " -C " + get_install()).c_str()) == EXIT_SUCCESS;
+#    else  // !USE_SHELL_API
+    const char prog[] = {"/usr/bin/tar"};
+    const char*const args[] =
+    {
+        prog, "-xzf", gz_file.c_str(), "-C", get_install().c_str(), nullptr
+    };
+    bool unzipped = (run_program(prog, args) == EXIT_SUCCESS);
+#    endif // !USE_SHELL_API
+    if (unzipped)
+    {
+        delete_file(gz_file);
+        return true;
+    }
+    return false;
+}
+
+#  endif // !_WIN32
+
+bool
+remote_download(const std::string& version, char* error_buffer)
+{
+    assert(!version.empty());
+
+#  ifdef _WIN32
+    // Download folder should be always available for Windows
+#  else  // !_WIN32
+    // Create download folder if it does not exist on UNIX system
+    auto download_folder = get_install();
+    if (!file_exists(download_folder))
+    {
+        if (!make_directory(download_folder))
+            return false;
+    }
+#  endif  // _WIN32
+
+    auto url = "https://data.iana.org/time-zones/releases/tzdata" + version +
+               ".tar.gz";
+    bool result = download_to_file(url, get_download_gz_file(version),
+                                   download_file_options::binary, error_buffer);
+#  ifdef _WIN32
+    if (result)
+    {
+        auto mapping_file = get_download_mapping_file(version);
+        result = download_to_file(
+			"https://raw.githubusercontent.com/unicode-org/cldr/master/"
+			"common/supplemental/windowsZones.xml",
+            mapping_file, download_file_options::text, error_buffer);
+    }
+#  endif  // _WIN32
+    return result;
+}
+
+bool
+remote_install(const std::string& version)
+{
+    auto success = false;
+    assert(!version.empty());
+
+    std::string install = get_install();
+    auto gz_file = get_download_gz_file(version);
+    if (file_exists(gz_file))
+    {
+        if (file_exists(install))
+            remove_folder_and_subfolders(install);
+        if (make_directory(install))
+        {
+            if (extract_gz_file(version, gz_file, install))
+                success = true;
+#  ifdef _WIN32
+            auto mapping_file_source = get_download_mapping_file(version);
+            auto mapping_file_dest = get_install();
+            mapping_file_dest += folder_delimiter;
+            mapping_file_dest += "windowsZones.xml";
+            if (!move_file(mapping_file_source, mapping_file_dest))
+                success = false;
+#  endif  // _WIN32
+        }
+    }
+    return success;
+}
+
+#endif  // HAS_REMOTE_API
+
+static
+std::string
+get_version(const std::string& path)
+{
+    std::string version;
+    std::ifstream infile(path + "version");
+    if (infile.is_open())
+    {
+        infile >> version;
+        if (!infile.fail())
+            return version;
+    }
+    else
+    {
+        infile.open(path + "NEWS");
+        while (infile)
+        {
+            infile >> version;
+            if (version == "Release")
+            {
+                infile >> version;
+                return version;
+            }
+        }
+    }
+    throw std::runtime_error("Unable to get Timezone database version from " + path);
+}
+
+static
+std::unique_ptr<tzdb>
+init_tzdb()
+{
+    using namespace date;
+    const std::string install = get_install();
+    const std::string path = install + folder_delimiter;
+    std::string line;
+    bool continue_zone = false;
+    std::unique_ptr<tzdb> db(new tzdb);
+
+#if AUTO_DOWNLOAD
+    if (!file_exists(install))
+    {
+        auto rv = remote_version();
+        if (!rv.empty() && remote_download(rv))
+        {
+            if (!remote_install(rv))
+            {
+                std::string msg = "Timezone database version \"";
+                msg += rv;
+                msg += "\" did not install correctly to \"";
+                msg += install;
+                msg += "\"";
+                throw std::runtime_error(msg);
+            }
+        }
+        if (!file_exists(install))
+        {
+            std::string msg = "Timezone database not found at \"";
+            msg += install;
+            msg += "\"";
+            throw std::runtime_error(msg);
+        }
+        db->version = get_version(path);
+    }
+    else
+    {
+        db->version = get_version(path);
+        auto rv = remote_version();
+        if (!rv.empty() && db->version != rv)
+        {
+            if (remote_download(rv))
+            {
+                remote_install(rv);
+                db->version = get_version(path);
+            }
+        }
+    }
+#else  // !AUTO_DOWNLOAD
+    if (!file_exists(install))
+    {
+        std::string msg = "Timezone database not found at \"";
+        msg += install;
+        msg += "\"";
+        throw std::runtime_error(msg);
+    }
+    db->version = get_version(path);
+#endif  // !AUTO_DOWNLOAD
+
+    CONSTDATA char*const files[] =
+    {
+        "africa", "antarctica", "asia", "australasia", "backward", "etcetera", "europe",
+        "pacificnew", "northamerica", "southamerica", "systemv", "leapseconds"
+    };
+
+    for (const auto& filename : files)
+    {
+        std::ifstream infile(path + filename);
+        while (infile)
+        {
+            std::getline(infile, line);
+            if (!line.empty() && line[0] != '#')
+            {
+                std::istringstream in(line);
+                std::string word;
+                in >> word;
+                if (word == "Rule")
+                {
+                    db->rules.push_back(Rule(line));
+                    continue_zone = false;
+                }
+                else if (word == "Link")
+                {
+                    db->links.push_back(time_zone_link(line));
+                    continue_zone = false;
+                }
+                else if (word == "Leap")
+                {
+                    db->leap_seconds.push_back(leap_second(line, detail::undocumented{}));
+                    continue_zone = false;
+                }
+                else if (word == "Zone")
+                {
+                    db->zones.push_back(time_zone(line, detail::undocumented{}));
+                    continue_zone = true;
+                }
+                else if (line[0] == '\t' && continue_zone)
+                {
+                    db->zones.back().add(line);
+                }
+                else
+                {
+                    std::cerr << line << '\n';
+                }
+            }
+        }
+    }
+    std::sort(db->rules.begin(), db->rules.end());
+    Rule::split_overlaps(db->rules);
+    std::sort(db->zones.begin(), db->zones.end());
+    db->zones.shrink_to_fit();
+    std::sort(db->links.begin(), db->links.end());
+    db->links.shrink_to_fit();
+    std::sort(db->leap_seconds.begin(), db->leap_seconds.end());
+    db->leap_seconds.shrink_to_fit();
+
+#ifdef _WIN32
+    std::string mapping_file = get_install() + folder_delimiter + "windowsZones.xml";
+    db->mappings = load_timezone_mappings_from_xml_file(mapping_file);
+    sort_zone_mappings(db->mappings);
+#endif // _WIN32
+
+    return db;
+}
+
+const tzdb&
+reload_tzdb()
+{
+#if AUTO_DOWNLOAD
+    auto const& v = get_tzdb_list().front().version;
+    if (!v.empty() && v == remote_version())
+        return get_tzdb_list().front();
+#endif  // AUTO_DOWNLOAD
+    tzdb_list::undocumented_helper::push_front(get_tzdb_list(), init_tzdb().release());
+    return get_tzdb_list().front();
+}
+
+#endif  // !USE_OS_TZDB
+
+const tzdb&
+get_tzdb()
+{
+    return get_tzdb_list().front();
+}
+
+const time_zone*
+#if HAS_STRING_VIEW
+tzdb::locate_zone(std::string_view tz_name) const
+#else
+tzdb::locate_zone(const std::string& tz_name) const
+#endif
+{
+    auto zi = std::lower_bound(zones.begin(), zones.end(), tz_name,
+#if HAS_STRING_VIEW
+        [](const time_zone& z, const std::string_view& nm)
+#else
+        [](const time_zone& z, const std::string& nm)
+#endif
+        {
+            return z.name() < nm;
+        });
+    if (zi == zones.end() || zi->name() != tz_name)
+    {
+#if !USE_OS_TZDB
+        auto li = std::lower_bound(links.begin(), links.end(), tz_name,
+#if HAS_STRING_VIEW
+        [](const time_zone_link& z, const std::string_view& nm)
+#else
+        [](const time_zone_link& z, const std::string& nm)
+#endif
+        {
+            return z.name() < nm;
+        });
+        if (li != links.end() && li->name() == tz_name)
+        {
+            zi = std::lower_bound(zones.begin(), zones.end(), li->target(),
+                [](const time_zone& z, const std::string& nm)
+                {
+                    return z.name() < nm;
+                });
+            if (zi != zones.end() && zi->name() == li->target())
+                return &*zi;
+        }
+#endif  // !USE_OS_TZDB
+        throw std::runtime_error(std::string(tz_name) + " not found in timezone database");
+    }
+    return &*zi;
+}
+
+const time_zone*
+#if HAS_STRING_VIEW
+locate_zone(std::string_view tz_name)
+#else
+locate_zone(const std::string& tz_name)
+#endif
+{
+    return get_tzdb().locate_zone(tz_name);
+}
+
+#if USE_OS_TZDB
+
+std::ostream&
+operator<<(std::ostream& os, const tzdb& db)
+{
+    os << "Version: " << db.version << "\n\n";
+    for (const auto& x : db.zones)
+        os << x << '\n';
+#if !MISSING_LEAP_SECONDS
+    os << '\n';
+    for (const auto& x : db.leap_seconds)
+        os << x << '\n';
+#endif  // !MISSING_LEAP_SECONDS
+    return os;
+}
+
+#else  // !USE_OS_TZDB
+
+std::ostream&
+operator<<(std::ostream& os, const tzdb& db)
+{
+    os << "Version: " << db.version << '\n';
+    std::string title("--------------------------------------------"
+                      "--------------------------------------------\n"
+                      "Name           ""Start Y ""End Y   "
+                      "Beginning                              ""Offset  "
+                      "Designator\n"
+                      "--------------------------------------------"
+                      "--------------------------------------------\n");
+    int count = 0;
+    for (const auto& x : db.rules)
+    {
+        if (count++ % 50 == 0)
+            os << title;
+        os << x << '\n';
+    }
+    os << '\n';
+    title = std::string("---------------------------------------------------------"
+                        "--------------------------------------------------------\n"
+                        "Name                               ""Offset      "
+                        "Rule           ""Abrev      ""Until\n"
+                        "---------------------------------------------------------"
+                        "--------------------------------------------------------\n");
+    count = 0;
+    for (const auto& x : db.zones)
+    {
+        if (count++ % 10 == 0)
+            os << title;
+        os << x << '\n';
+    }
+    os << '\n';
+    title = std::string("---------------------------------------------------------"
+                        "--------------------------------------------------------\n"
+                        "Alias                                   ""To\n"
+                        "---------------------------------------------------------"
+                        "--------------------------------------------------------\n");
+    count = 0;
+    for (const auto& x : db.links)
+    {
+        if (count++ % 45 == 0)
+            os << title;
+        os << x << '\n';
+    }
+    os << '\n';
+    title = std::string("---------------------------------------------------------"
+                        "--------------------------------------------------------\n"
+                        "Leap second on\n"
+                        "---------------------------------------------------------"
+                        "--------------------------------------------------------\n");
+    os << title;
+    for (const auto& x : db.leap_seconds)
+        os << x << '\n';
+    return os;
+}
+
+#endif  // !USE_OS_TZDB
+
+// -----------------------
+
+#ifdef _WIN32
+
+static
+std::string
+getTimeZoneKeyName()
+{
+    DYNAMIC_TIME_ZONE_INFORMATION dtzi{};
+    auto result = GetDynamicTimeZoneInformation(&dtzi);
+    if (result == TIME_ZONE_ID_INVALID)
+        throw std::runtime_error("current_zone(): GetDynamicTimeZoneInformation()"
+                                 " reported TIME_ZONE_ID_INVALID.");
+    auto wlen = wcslen(dtzi.TimeZoneKeyName);
+    char buf[128] = {};
+    assert(sizeof(buf) >= wlen+1);
+    wcstombs(buf, dtzi.TimeZoneKeyName, wlen);
+    if (strcmp(buf, "Coordinated Universal Time") == 0)
+        return "UTC";
+    return buf;
+}
+
+const time_zone*
+tzdb::current_zone() const
+{
+    std::string win_tzid = getTimeZoneKeyName();
+    std::string standard_tzid;
+    if (!native_to_standard_timezone_name(win_tzid, standard_tzid))
+    {
+        std::string msg;
+        msg = "current_zone() failed: A mapping from the Windows Time Zone id \"";
+        msg += win_tzid;
+        msg += "\" was not found in the time zone mapping database.";
+        throw std::runtime_error(msg);
+    }
+    return locate_zone(standard_tzid);
+}
+
+#else  // !_WIN32
+
+const time_zone*
+tzdb::current_zone() const
+{
+    // On some OS's a file called /etc/localtime may
+    // exist and it may be either a real file
+    // containing time zone details or a symlink to such a file.
+    // On MacOS and BSD Unix if this file is a symlink it
+    // might resolve to a path like this:
+    // "/usr/share/zoneinfo/America/Los_Angeles"
+    // If it does, we try to determine the current
+    // timezone from the remainder of the path by removing the prefix
+    // and hoping the rest resolves to a valid timezone.
+    // It may not always work though. If it doesn't then an
+    // exception will be thrown by local_timezone.
+    // The path may also take a relative form:
+    // "../usr/share/zoneinfo/America/Los_Angeles".
+    {
+        struct stat sb;
+        CONSTDATA auto timezone = "/etc/localtime";
+        if (lstat(timezone, &sb) == 0 && S_ISLNK(sb.st_mode) && sb.st_size > 0) {
+            using namespace std;
+            char rp[PATH_MAX+1] = {};
+            if (realpath(timezone, rp) == nullptr)
+                throw system_error(errno, system_category(), "realpath() failed");
+#if HAS_STRING_VIEW
+            string_view result = rp;
+            CONSTDATA string_view zoneinfo = "zoneinfo";
+            size_t pos = result.rfind(zoneinfo);
+            if (pos == result.npos)
+                throw runtime_error(
+                    "current_zone() failed to find \"zoneinfo\" in " + string(result));
+            pos = result.find('/', pos);
+            result.remove_prefix(pos + 1);
+#else
+            string result = rp;
+            CONSTDATA char zoneinfo[] = "zoneinfo";
+            size_t pos = result.rfind(zoneinfo);
+            if (pos == result.npos)
+                throw runtime_error(
+                    "current_zone() failed to find \"zoneinfo\" in " + result);
+            pos = result.find('/', pos);
+            result.erase(0, pos + 1);
+#endif
+            return locate_zone(result);
+        }
+    }
+    // On embedded systems e.g. buildroot with uclibc the timezone is linked
+    // into /etc/TZ which is a symlink to path like this:
+    // "/usr/share/zoneinfo/uclibc/America/Los_Angeles"
+    // If it does, we try to determine the current
+    // timezone from the remainder of the path by removing the prefix
+    // and hoping the rest resolves to valid timezone.
+    // It may not always work though. If it doesn't then an
+    // exception will be thrown by local_timezone.
+    // The path may also take a relative form:
+    // "../usr/share/zoneinfo/uclibc/America/Los_Angeles".
+    {
+        struct stat sb;
+        CONSTDATA auto timezone = "/etc/TZ";
+        if (lstat(timezone, &sb) == 0 && S_ISLNK(sb.st_mode) && sb.st_size > 0) {
+            using namespace std;
+            string result;
+            char rp[PATH_MAX+1] = {};
+            if (readlink(timezone, rp, sizeof(rp)-1) > 0)
+                result = string(rp);
+            else
+                throw system_error(errno, system_category(), "readlink() failed");
+
+            const size_t pos = result.find(get_tz_dir());
+            if (pos != result.npos)
+                result.erase(0, get_tz_dir().size() + 1 + pos);
+            return locate_zone(result);
+        }
+    }
+    {
+    // On some versions of some linux distro's (e.g. Ubuntu),
+    // the current timezone might be in the first line of
+    // the /etc/timezone file.
+        std::ifstream timezone_file("/etc/timezone");
+        if (timezone_file.is_open())
+        {
+            std::string result;
+            std::getline(timezone_file, result);
+            if (!result.empty())
+                return locate_zone(result);
+        }
+        // Fall through to try other means.
+    }
+    {
+    // On some versions of some bsd distro's (e.g. FreeBSD),
+    // the current timezone might be in the first line of
+    // the /var/db/zoneinfo file.
+        std::ifstream timezone_file("/var/db/zoneinfo");
+        if (timezone_file.is_open())
+        {
+            std::string result;
+            std::getline(timezone_file, result);
+            if (!result.empty())
+                return locate_zone(result);
+        }
+        // Fall through to try other means.
+    }
+    {
+    // On some versions of some bsd distro's (e.g. iOS),
+    // it is not possible to use file based approach,
+    // we switch to system API, calling functions in
+    // CoreFoundation framework.
+#if TARGET_OS_IPHONE
+        std::string result = date::iOSUtils::get_current_timezone();
+        if (!result.empty())
+            return locate_zone(result);
+#endif
+    // Fall through to try other means.
+    }
+    {
+    // On some versions of some linux distro's (e.g. Red Hat),
+    // the current timezone might be in the first line of
+    // the /etc/sysconfig/clock file as:
+    // ZONE="US/Eastern"
+        std::ifstream timezone_file("/etc/sysconfig/clock");
+        std::string result;
+        while (timezone_file)
+        {
+            std::getline(timezone_file, result);
+            auto p = result.find("ZONE=\"");
+            if (p != std::string::npos)
+            {
+                result.erase(p, p+6);
+                result.erase(result.rfind('"'));
+                return locate_zone(result);
+            }
+        }
+        // Fall through to try other means.
+    }
+    throw std::runtime_error("Could not get current timezone");
+}
+
+#endif  // !_WIN32
+
+const time_zone*
+current_zone()
+{
+    return get_tzdb().current_zone();
+}
+
+}  // namespace date
+
+#if defined(__GNUC__) && __GNUC__ < 5
+# pragma GCC diagnostic pop
+#endif