From: Mark de Wever <koraq@xs4all.nl>
Date: Thu, 20 Apr 2023 19:40:36 +0000 (+0200)
Subject: [libc++][chrono] Adds formatter file_time.
X-Git-Tag: upstream/17.0.6~10180
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=96f303324f58a58a7e58d75f797793c66606e745;p=platform%2Fupstream%2Fllvm.git

[libc++][chrono] Adds formatter file_time.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D148928
---

diff --git a/libcxx/docs/Status/FormatPaper.csv b/libcxx/docs/Status/FormatPaper.csv
index 2cd430f..260cd2f 100644
--- a/libcxx/docs/Status/FormatPaper.csv
+++ b/libcxx/docs/Status/FormatPaper.csv
@@ -5,7 +5,7 @@ Section,Description,Dependencies,Assignee,Status,First released version
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::utc_time<Duration>``",A ``<chrono>`` implementation,Not assigned,,,
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::tai_time<Duration>``",A ``<chrono>`` implementation,Not assigned,,,
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::gps_time<Duration>``",A ``<chrono>`` implementation,Not assigned,,,
-`[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::file_time<Duration>``",,Mark de Wever,|In Progress|,,
+`[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::file_time<Duration>``",,Mark de Wever,|Complete|, Clang 17
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::local_time<Duration>``",,Mark de Wever,|In Progress|,,
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::local-time-format-t<Duration>``",A ``<chrono>`` implementation,Not assigned,,,
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::day``",,Mark de Wever,|Complete|, Clang 16
diff --git a/libcxx/include/__chrono/convert_to_tm.h b/libcxx/include/__chrono/convert_to_tm.h
index 95cde20..a453cba 100644
--- a/libcxx/include/__chrono/convert_to_tm.h
+++ b/libcxx/include/__chrono/convert_to_tm.h
@@ -13,6 +13,7 @@
 #include <__chrono/concepts.h>
 #include <__chrono/day.h>
 #include <__chrono/duration.h>
+#include <__chrono/file_clock.h>
 #include <__chrono/hh_mm_ss.h>
 #include <__chrono/month.h>
 #include <__chrono/month_weekday.h>
@@ -73,6 +74,24 @@ _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const _Date& __date, chrono::weekday _
   return __result;
 }
 
+template <class _Tm, class _Duration>
+_LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const chrono::sys_time<_Duration> __tp) {
+  chrono::sys_days __days = chrono::time_point_cast<chrono::days>(__tp);
+  chrono::year_month_day __ymd{__days};
+
+  _Tm __result = std::__convert_to_tm<_Tm>(chrono::year_month_day{__ymd}, chrono::weekday{__days});
+
+  uint64_t __sec =
+      chrono::duration_cast<chrono::seconds>(__tp - chrono::time_point_cast<chrono::seconds>(__days)).count();
+  __sec %= 24 * 3600;
+  __result.tm_hour = __sec / 3600;
+  __sec %= 3600;
+  __result.tm_min = __sec / 60;
+  __result.tm_sec = __sec % 60;
+
+  return __result;
+}
+
 // Convert a chrono (calendar) time point, or dururation to the given _Tm type,
 // which must have the same properties as std::tm.
 template <class _Tm, class _ChronoT>
@@ -83,22 +102,11 @@ _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const _ChronoT& __value) {
 #  endif
 
   if constexpr (__is_time_point<_ChronoT>) {
-    if constexpr (same_as<typename _ChronoT::clock, chrono::system_clock>) {
-      chrono::sys_days __days = chrono::time_point_cast<chrono::days>(__value);
-      chrono::year_month_day __ymd{__days};
-
-      __result = std::__convert_to_tm<_Tm>(chrono::year_month_day{__ymd}, chrono::weekday{__days});
-
-      // TODO FMT D138826 has improvements for this part.
-      // TODO FMT Since this is identical for duration and system time it would be good to avoid code duplication.
-      uint64_t __sec =
-          chrono::duration_cast<chrono::seconds>(__value - chrono::time_point_cast<chrono::seconds>(__days)).count();
-      __sec %= 24 * 3600;
-      __result.tm_hour = __sec / 3600;
-      __sec %= 3600;
-      __result.tm_min = __sec / 60;
-      __result.tm_sec = __sec % 60;
-    } else
+    if constexpr (same_as<typename _ChronoT::clock, chrono::system_clock>)
+      return std::__convert_to_tm<_Tm>(__value);
+    else if constexpr (same_as<typename _ChronoT::clock, chrono::file_clock>)
+      return std::__convert_to_tm<_Tm>(_ChronoT::clock::to_sys(__value));
+    else
       static_assert(sizeof(_ChronoT) == 0, "TODO: Add the missing clock specialization");
   } else if constexpr (chrono::__is_duration<_ChronoT>::value) {
     // [time.format]/6
diff --git a/libcxx/include/__chrono/formatter.h b/libcxx/include/__chrono/formatter.h
index e73b043..5b10d67 100644
--- a/libcxx/include/__chrono/formatter.h
+++ b/libcxx/include/__chrono/formatter.h
@@ -15,6 +15,7 @@
 #include <__chrono/convert_to_tm.h>
 #include <__chrono/day.h>
 #include <__chrono/duration.h>
+#include <__chrono/file_clock.h>
 #include <__chrono/hh_mm_ss.h>
 #include <__chrono/month.h>
 #include <__chrono/month_weekday.h>
@@ -591,6 +592,17 @@ public:
   }
 };
 
+template <class _Duration, __fmt_char_type _CharT>
+struct _LIBCPP_TEMPLATE_VIS formatter<chrono::file_time<_Duration>, _CharT> : public __formatter_chrono<_CharT> {
+public:
+  using _Base = __formatter_chrono<_CharT>;
+
+  _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
+      -> decltype(__parse_ctx.begin()) {
+    return _Base::__parse(__parse_ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
+  }
+};
+
 template <class _Rep, class _Period, __fmt_char_type _CharT>
 struct formatter<chrono::duration<_Rep, _Period>, _CharT> : public __formatter_chrono<_CharT> {
 public:
diff --git a/libcxx/include/__chrono/ostream.h b/libcxx/include/__chrono/ostream.h
index 26df882..b1a2fb1 100644
--- a/libcxx/include/__chrono/ostream.h
+++ b/libcxx/include/__chrono/ostream.h
@@ -12,6 +12,7 @@
 
 #include <__chrono/day.h>
 #include <__chrono/duration.h>
+#include <__chrono/file_clock.h>
 #include <__chrono/hh_mm_ss.h>
 #include <__chrono/month.h>
 #include <__chrono/month_weekday.h>
@@ -45,6 +46,12 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, const sys_time<_Duration> __tp)
   return __os << std::format(__os.getloc(), _LIBCPP_STATICALLY_WIDEN(_CharT, "{:L%F %T}"), __tp);
 }
 
+template <class _CharT, class _Traits, class _Duration>
+_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits>& __os, const file_time<_Duration> __tp) {
+  return __os << std::format(__os.getloc(), _LIBCPP_STATICALLY_WIDEN(_CharT, "{:L%F %T}"), __tp);
+}
+
 // Depending on the type the return is a const _CharT* or a basic_string<_CharT>
 template <class _CharT, class _Period>
 _LIBCPP_HIDE_FROM_ABI auto __units_suffix() {
diff --git a/libcxx/test/std/time/time.clock/time.clock.file/ostream.pass.cpp b/libcxx/test/std/time/time.clock/time.clock.file/ostream.pass.cpp
new file mode 100644
index 0000000..759387b
--- /dev/null
+++ b/libcxx/test/std/time/time.clock/time.clock.file/ostream.pass.cpp
@@ -0,0 +1,200 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-localization
+// UNSUPPORTED: libcpp-has-no-incomplete-format
+
+// TODO FMT Investigate Windows issues.
+// UNSUPPORTED msvc, target={{.+}}-windows-gnu
+// TODO FMT It seems GCC uses too much memory in the CI and fails.
+// UNSUPPORTED: gcc-12
+
+// TODO FMT This test should not require std::to_chars(floating-point)
+// XFAIL: availability-fp_to_chars-missing
+
+// REQUIRES: locale.fr_FR.UTF-8
+// REQUIRES: locale.ja_JP.UTF-8
+
+// <chrono>
+
+// class system_clock;
+
+// template<class charT, class traits, class Duration>
+//   basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const sys_time<Duration>& tp);
+
+#include <chrono>
+#include <cassert>
+#include <ratio>
+#include <sstream>
+
+#include "make_string.h"
+#include "platform_support.h" // locale name macros
+#include "test_macros.h"
+
+#define SV(S) MAKE_STRING_VIEW(CharT, S)
+
+// Modeled after the system clock's usings, this make adapating the
+// tests easier.
+template <class Duration>
+using file_time    = std::chrono::time_point<std::chrono::file_clock, Duration>;
+using file_seconds = file_time<std::chrono::seconds>;
+using file_days    = file_time<std::chrono::days>;
+
+template <class CharT, class Duration>
+static std::basic_string<CharT> stream_c_locale(file_time<Duration> time_point) {
+  std::basic_stringstream<CharT> sstr;
+  sstr << std::fixed << time_point;
+  return sstr.str();
+}
+
+template <class CharT, class Duration>
+static std::basic_string<CharT> stream_fr_FR_locale(file_time<Duration> time_point) {
+  std::basic_stringstream<CharT> sstr;
+  const std::locale locale(LOCALE_fr_FR_UTF_8);
+  sstr.imbue(locale);
+  sstr << std::fixed << time_point;
+  return sstr.str();
+}
+
+template <class CharT, class Duration>
+static std::basic_string<CharT> stream_ja_JP_locale(file_time<Duration> time_point) {
+  std::basic_stringstream<CharT> sstr;
+  const std::locale locale(LOCALE_ja_JP_UTF_8);
+  sstr.imbue(locale);
+  sstr << std::fixed << time_point;
+  return sstr.str();
+}
+
+template <class CharT>
+static void test_c() {
+  using namespace std::literals::chrono_literals;
+
+  assert(stream_c_locale<CharT>(file_time<std::chrono::nanoseconds>{946'688'523'123'456'789ns}) ==
+         SV("2000-01-01 01:02:03.123456789"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::microseconds>{946'688'523'123'456us}) ==
+         SV("2000-01-01 01:02:03.123456"));
+
+  assert(stream_c_locale<CharT>(file_time<std::chrono::milliseconds>{946'684'800'123ms}) ==
+         SV("2000-01-01 00:00:00.123"));
+  assert(stream_c_locale<CharT>(file_seconds{1'234'567'890s}) == SV("2009-02-13 23:31:30"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::minutes>{20'576'131min}) == SV("2009-02-13 23:31:00"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::hours>{342'935h}) == SV("2009-02-13 23:00:00"));
+  assert(stream_c_locale<CharT>(file_days{std::chrono::days{14'288}}) == SV("2009-02-13 00:00:00"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::weeks>{std::chrono::weeks{2041}}) == SV("2009-02-12 00:00:00"));
+
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<signed char, std::ratio<2, 1>>>{
+             std::chrono::duration<signed char, std::ratio<2, 1>>{60}}) == SV("1970-01-01 00:02:00"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<short, std::ratio<1, 2>>>{
+             std::chrono::duration<short, std::ratio<1, 2>>{3600}}) == SV("1970-01-01 00:30:00.0"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<int, std::ratio<1, 4>>>{
+             std::chrono::duration<int, std::ratio<1, 4>>{3600}}) == SV("1970-01-01 00:15:00.00"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<long, std::ratio<1, 10>>>{
+             std::chrono::duration<long, std::ratio<1, 10>>{36611}}) == SV("1970-01-01 01:01:01.1"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<long long, std::ratio<1, 100>>>{
+             std::chrono::duration<long long, std::ratio<1, 100>>{12'345'678'9010}}) == SV("2009-02-13 23:31:30.10"));
+
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<float, std::ratio<1, 1>>>{
+             std::chrono::duration<float, std::ratio<1, 1>>{123.456}}) == SV("1970-01-01 00:02:03"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<double, std::ratio<1, 10>>>{
+             std::chrono::duration<double, std::ratio<1, 10>>{123.456}}) == SV("1970-01-01 00:00:12.3"));
+  assert(stream_c_locale<CharT>(file_time<std::chrono::duration<long double, std::ratio<1, 100>>>{
+             std::chrono::duration<long double, std::ratio<1, 100>>{123.456}}) == SV("1970-01-01 00:00:01.23"));
+}
+
+template <class CharT>
+static void test_fr_FR() {
+  using namespace std::literals::chrono_literals;
+
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::nanoseconds>{946'688'523'123'456'789ns}) ==
+         SV("2000-01-01 01:02:03,123456789"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::microseconds>{946'688'523'123'456us}) ==
+         SV("2000-01-01 01:02:03,123456"));
+
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::milliseconds>{946'684'800'123ms}) ==
+         SV("2000-01-01 00:00:00,123"));
+  assert(stream_fr_FR_locale<CharT>(file_seconds{1'234'567'890s}) == SV("2009-02-13 23:31:30"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::minutes>{20'576'131min}) == SV("2009-02-13 23:31:00"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::hours>{342'935h}) == SV("2009-02-13 23:00:00"));
+  assert(stream_fr_FR_locale<CharT>(file_days{std::chrono::days{14'288}}) == SV("2009-02-13 00:00:00"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::weeks>{std::chrono::weeks{2041}}) ==
+         SV("2009-02-12 00:00:00"));
+
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<signed char, std::ratio<2, 1>>>{
+             std::chrono::duration<signed char, std::ratio<2, 1>>{60}}) == SV("1970-01-01 00:02:00"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<short, std::ratio<1, 2>>>{
+             std::chrono::duration<short, std::ratio<1, 2>>{3600}}) == SV("1970-01-01 00:30:00,0"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<int, std::ratio<1, 4>>>{
+             std::chrono::duration<int, std::ratio<1, 4>>{3600}}) == SV("1970-01-01 00:15:00,00"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<long, std::ratio<1, 10>>>{
+             std::chrono::duration<long, std::ratio<1, 10>>{36611}}) == SV("1970-01-01 01:01:01,1"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<long long, std::ratio<1, 100>>>{
+             std::chrono::duration<long long, std::ratio<1, 100>>{12'345'678'9010}}) == SV("2009-02-13 23:31:30,10"));
+
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<float, std::ratio<1, 1>>>{
+             std::chrono::duration<float, std::ratio<1, 1>>{123.456}}) == SV("1970-01-01 00:02:03"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<double, std::ratio<1, 10>>>{
+             std::chrono::duration<double, std::ratio<1, 10>>{123.456}}) == SV("1970-01-01 00:00:12,3"));
+  assert(stream_fr_FR_locale<CharT>(file_time<std::chrono::duration<long double, std::ratio<1, 100>>>{
+             std::chrono::duration<long double, std::ratio<1, 100>>{123.456}}) == SV("1970-01-01 00:00:01,23"));
+}
+
+template <class CharT>
+static void test_ja_JP() {
+  using namespace std::literals::chrono_literals;
+
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::nanoseconds>{946'688'523'123'456'789ns}) ==
+         SV("2000-01-01 01:02:03.123456789"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::microseconds>{946'688'523'123'456us}) ==
+         SV("2000-01-01 01:02:03.123456"));
+
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::milliseconds>{946'684'800'123ms}) ==
+         SV("2000-01-01 00:00:00.123"));
+  assert(stream_ja_JP_locale<CharT>(file_seconds{1'234'567'890s}) == SV("2009-02-13 23:31:30"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::minutes>{20'576'131min}) == SV("2009-02-13 23:31:00"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::hours>{342'935h}) == SV("2009-02-13 23:00:00"));
+  assert(stream_ja_JP_locale<CharT>(file_days{std::chrono::days{14'288}}) == SV("2009-02-13 00:00:00"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::weeks>{std::chrono::weeks{2041}}) ==
+         SV("2009-02-12 00:00:00"));
+
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<signed char, std::ratio<2, 1>>>{
+             std::chrono::duration<signed char, std::ratio<2, 1>>{60}}) == SV("1970-01-01 00:02:00"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<short, std::ratio<1, 2>>>{
+             std::chrono::duration<short, std::ratio<1, 2>>{3600}}) == SV("1970-01-01 00:30:00.0"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<int, std::ratio<1, 4>>>{
+             std::chrono::duration<int, std::ratio<1, 4>>{3600}}) == SV("1970-01-01 00:15:00.00"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<long, std::ratio<1, 10>>>{
+             std::chrono::duration<long, std::ratio<1, 10>>{36611}}) == SV("1970-01-01 01:01:01.1"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<long long, std::ratio<1, 100>>>{
+             std::chrono::duration<long long, std::ratio<1, 100>>{12'345'678'9010}}) == SV("2009-02-13 23:31:30.10"));
+
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<float, std::ratio<1, 1>>>{
+             std::chrono::duration<float, std::ratio<1, 1>>{123.456}}) == SV("1970-01-01 00:02:03"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<double, std::ratio<1, 10>>>{
+             std::chrono::duration<double, std::ratio<1, 10>>{123.456}}) == SV("1970-01-01 00:00:12.3"));
+  assert(stream_ja_JP_locale<CharT>(file_time<std::chrono::duration<long double, std::ratio<1, 100>>>{
+             std::chrono::duration<long double, std::ratio<1, 100>>{123.456}}) == SV("1970-01-01 00:00:01.23"));
+}
+
+template <class CharT>
+static void test() {
+  test_c<CharT>();
+  test_fr_FR<CharT>();
+  test_ja_JP<CharT>();
+}
+
+int main(int, char**) {
+  test<char>();
+
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  test<wchar_t>();
+#endif
+
+  return 0;
+}
diff --git a/libcxx/test/std/time/time.syn/formatter.file_time.pass.cpp b/libcxx/test/std/time/time.syn/formatter.file_time.pass.cpp
new file mode 100644
index 0000000..8cc8ecf
--- /dev/null
+++ b/libcxx/test/std/time/time.syn/formatter.file_time.pass.cpp
@@ -0,0 +1,940 @@
+//===----------------------------------------------------------------------===//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-localization
+// UNSUPPORTED: libcpp-has-no-incomplete-format
+
+// XFAIL: LIBCXX-FREEBSD-FIXME
+
+// TODO FMT This test should not require std::to_chars(floating-point)
+// XFAIL: availability-fp_to_chars-missing
+
+// TODO FMT Investigate Windows issues.
+// UNSUPPORTED: msvc, target={{.+}}-windows-gnu
+// TODO FMT It seems GCC uses too much memory in the CI and fails.
+// UNSUPPORTED: gcc-12
+
+// REQUIRES: locale.fr_FR.UTF-8
+// REQUIRES: locale.ja_JP.UTF-8
+
+// <chrono>
+//
+// template<class charT> struct formatter<chrono::file_time, charT>;
+
+#include <chrono>
+#include <format>
+
+#include <cassert>
+#include <concepts>
+#include <locale>
+#include <iostream>
+#include <type_traits>
+
+#include "formatter_tests.h"
+#include "make_string.h"
+#include "platform_support.h" // locale name macros
+#include "test_macros.h"
+
+// Modeled after the system clock's usings, this make adapting the
+// tests easier.
+template <class Duration>
+using file_time    = std::chrono::time_point<std::chrono::file_clock, Duration>;
+using file_seconds = file_time<std::chrono::seconds>;
+using file_days    = file_time<std::chrono::days>;
+
+template <class CharT>
+static void test_no_chrono_specs() {
+  using namespace std::literals::chrono_literals;
+
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output
+  check(SV("1970-01-01 00:00:00"), SV("{}"), file_seconds(0s));
+  check(SV("2000-01-01 00:00:00"), SV("{}"), file_seconds(946'684'800s));
+  check(SV("2000-01-01 01:02:03"), SV("{}"), file_seconds(946'688'523s));
+
+  check(SV("2000-01-01 01:02:03.123"), SV("{}"), file_time<std::chrono::milliseconds>(946'688'523'123ms));
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_year() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt =
+      SV("{:%%C='%C'%t%%EC='%EC'%t%%y='%y'%t%%Oy='%Oy'%t%%Ey='%Ey'%t%%Y='%Y'%t%%EY='%EY'%n}");
+  constexpr std::basic_string_view<CharT> lfmt =
+      SV("{:L%%C='%C'%t%%EC='%EC'%t%%y='%y'%t%%Oy='%Oy'%t%%Ey='%Ey'%t%%Y='%Y'%t%%EY='%EY'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%C='19'\t%EC='19'\t%y='70'\t%Oy='70'\t%Ey='70'\t%Y='1970'\t%EY='1970'\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%C='20'\t%EC='20'\t%y='09'\t%Oy='09'\t%Ey='09'\t%Y='2009'\t%EY='2009'\n"),
+        fmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use the global locale (fr_FR)
+  check(SV("%C='19'\t%EC='19'\t%y='70'\t%Oy='70'\t%Ey='70'\t%Y='1970'\t%EY='1970'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%C='20'\t%EC='20'\t%y='09'\t%Oy='09'\t%Ey='09'\t%Y='2009'\t%EY='2009'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+#if defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%C='19'\t%EC='19'\t%y='70'\t%Oy='70'\t%Ey='70'\t%Y='1970'\t%EY='1970'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%C='20'\t%EC='20'\t%y='09'\t%Oy='09'\t%Ey='09'\t%Y='2009'\t%EY='2009'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else                                  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%C='19'\t%EC='昭和'\t%y='70'\t%Oy='七十'\t%Ey='45'\t%Y='1970'\t%EY='昭和45年'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%C='20'\t%EC='平成'\t%y='09'\t%Oy='九'\t%Ey='21'\t%Y='2009'\t%EY='平成21年'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif                                 // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_month() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%b='%b'%t%%h='%h'%t%%B='%B'%t%%m='%m'%t%%Om='%Om'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%b='%b'%t%%h='%h'%t%%B='%B'%t%%m='%m'%t%%Om='%Om'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%b='Jan'\t%h='Jan'\t%B='January'\t%m='01'\t%Om='01'\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%b='May'\t%h='May'\t%B='May'\t%m='05'\t%Om='05'\n"),
+        fmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+
+  // Use the global locale (fr_FR)
+#if defined(__APPLE__)
+  check(SV("%b='jan'\t%h='jan'\t%B='janvier'\t%m='01'\t%Om='01'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+#else
+  check(SV("%b='janv.'\t%h='janv.'\t%B='janvier'\t%m='01'\t%Om='01'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+#endif
+
+  check(SV("%b='mai'\t%h='mai'\t%B='mai'\t%m='05'\t%Om='05'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+#ifdef _WIN32
+  check(loc,
+        SV("%b='1'\t%h='1'\t%B='1月'\t%m='01'\t%Om='01'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%b='5'\t%h='5'\t%B='5月'\t%m='05'\t%Om='05'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#elif defined(_AIX)                    // _WIN32
+  check(loc,
+        SV("%b='1月'\t%h='1月'\t%B='1月'\t%m='01'\t%Om='01'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%b='5月'\t%h='5月'\t%B='5月'\t%m='05'\t%Om='05'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#elif defined(__APPLE__)               // _WIN32
+  check(loc,
+        SV("%b=' 1'\t%h=' 1'\t%B='1月'\t%m='01'\t%Om='01'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%b=' 5'\t%h=' 5'\t%B='5月'\t%m='05'\t%Om='05'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#else                                  // _WIN32
+  check(loc,
+        SV("%b=' 1月'\t%h=' 1月'\t%B='1月'\t%m='01'\t%Om='一'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%b=' 5月'\t%h=' 5月'\t%B='5月'\t%m='05'\t%Om='五'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#endif                                 // _WIN32
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_day() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%d='%d'%t%%Od='%Od'%t%%e='%e'%t%%Oe='%Oe'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%d='%d'%t%%Od='%Od'%t%%e='%e'%t%%Oe='%Oe'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%d='01'\t%Od='01'\t%e=' 1'\t%Oe=' 1'\n"), fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%d='13'\t%Od='13'\t%e='13'\t%Oe='13'\n"),
+        fmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use the global locale (fr_FR)
+  check(SV("%d='01'\t%Od='01'\t%e=' 1'\t%Oe=' 1'\n"), lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%d='13'\t%Od='13'\t%e='13'\t%Oe='13'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+#if defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%d='01'\t%Od='01'\t%e=' 1'\t%Oe=' 1'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%d='13'\t%Od='13'\t%e='13'\t%Oe='13'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else                                  // _WIN32
+  check(loc,
+        SV("%d='01'\t%Od='一'\t%e=' 1'\t%Oe='一'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%d='13'\t%Od='十三'\t%e='13'\t%Oe='十三'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+#endif                                 // _WIN32
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_weekday() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt =
+      SV("{:%%a='%a'%t%%A='%A'%t%%u='%u'%t%%Ou='%Ou'%t%%w='%w'%t%%Ow='%Ow'%n}");
+  constexpr std::basic_string_view<CharT> lfmt =
+      SV("{:L%%a='%a'%t%%A='%A'%t%%u='%u'%t%%Ou='%Ou'%t%%w='%w'%t%%Ow='%Ow'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%a='Thu'\t%A='Thursday'\t%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%a='Sun'\t%A='Sunday'\t%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\n"),
+        fmt,
+        file_seconds(4'294'967'295s)); // 06:28:15 UTC on Sunday, 7 February 2106
+
+  // Use the global locale (fr_FR)
+#if defined(__APPLE__)
+  check(SV("%a='Jeu'\t%A='Jeudi'\t%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%a='Dim'\t%A='Dimanche'\t%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\n"),
+        lfmt,
+        file_seconds(4'294'967'295s)); // 06:28:15 UTC on Sunday, 7 February 2106
+#else
+  check(SV("%a='jeu.'\t%A='jeudi'\t%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%a='dim.'\t%A='dimanche'\t%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\n"),
+        lfmt,
+        file_seconds(4'294'967'295s)); // 06:28:15 UTC on Sunday, 7 February 2106
+#endif
+
+  // Use supplied locale (ja_JP).
+  // This locale has a different alternate, but not on all platforms
+#if defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%a='木'\t%A='木曜日'\t%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%a='日'\t%A='日曜日'\t%u='7'\t%Ou='7'\t%w='0'\t%Ow='0'\n"),
+        lfmt,
+        file_seconds(4'294'967'295s)); // 06:28:15 UTC on Sunday, 7 February 2106
+#else                                  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%a='木'\t%A='木曜日'\t%u='4'\t%Ou='四'\t%w='4'\t%Ow='四'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%a='日'\t%A='日曜日'\t%u='7'\t%Ou='七'\t%w='0'\t%Ow='〇'\n"),
+        lfmt,
+        file_seconds(4'294'967'295s)); // 06:28:15 UTC on Sunday, 7 February 2106
+#endif                                 // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_day_of_year() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%j='%j'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%j='%j'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%j='001'\n"), fmt, file_seconds(0s));             // 00:00:00 UTC Thursday, 1 January 1970
+  check(SV("%j='138'\n"), fmt, file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+
+  // Use the global locale (fr_FR)
+  check(SV("%j='001'\n"), lfmt, file_seconds(0s));             // 00:00:00 UTC Thursday, 1 January 1970
+  check(SV("%j='138'\n"), lfmt, file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+  check(loc, SV("%j='001'\n"), lfmt, file_seconds(0s));             // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc, SV("%j='138'\n"), lfmt, file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_week() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%U='%U'%t%%OU='%OU'%t%%W='%W'%t%%OW='%OW'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%U='%U'%t%%OU='%OU'%t%%W='%W'%t%%OW='%OW'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%U='00'\t%OU='00'\t%W='00'\t%OW='00'\n"), fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%U='20'\t%OU='20'\t%W='20'\t%OW='20'\n"),
+        fmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+
+  // Use the global locale (fr_FR)
+  check(SV("%U='00'\t%OU='00'\t%W='00'\t%OW='00'\n"), lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%U='20'\t%OU='20'\t%W='20'\t%OW='20'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+#if defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%U='00'\t%OU='00'\t%W='00'\t%OW='00'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%U='20'\t%OU='20'\t%W='20'\t%OW='20'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#else                                  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%U='00'\t%OU='〇'\t%W='00'\t%OW='〇'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%U='20'\t%OU='二十'\t%W='20'\t%OW='二十'\n"),
+        lfmt,
+        file_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#endif                                 // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_iso_8601_week() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%g='%g'%t%%G='%G'%t%%V='%V'%t%%OV='%OV'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%g='%g'%t%%G='%G'%t%%V='%V'%t%%OV='%OV'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%g='70'\t%G='1970'\t%V='01'\t%OV='01'\n"), fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%g='09'\t%G='2009'\t%V='07'\t%OV='07'\n"),
+        fmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use the global locale (fr_FR)
+  check(SV("%g='70'\t%G='1970'\t%V='01'\t%OV='01'\n"), lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%g='09'\t%G='2009'\t%V='07'\t%OV='07'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+#if defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%g='70'\t%G='1970'\t%V='01'\t%OV='01'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%g='09'\t%G='2009'\t%V='07'\t%OV='07'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else                                  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%g='70'\t%G='1970'\t%V='01'\t%OV='一'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%g='09'\t%G='2009'\t%V='07'\t%OV='七'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif                                 // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_date() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%D='%D'%t%%F='%F'%t%%x='%x'%t%%Ex='%Ex'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%D='%D'%t%%F='%F'%t%%x='%x'%t%%Ex='%Ex'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%D='01/01/70'\t%F='1970-01-01'\t%x='01/01/70'\t%Ex='01/01/70'\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%D='02/13/09'\t%F='2009-02-13'\t%x='02/13/09'\t%Ex='02/13/09'\n"),
+        fmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use the global locale (fr_FR)
+#if defined(__APPLE__)
+  check(SV("%D='01/01/70'\t%F='1970-01-01'\t%x='01.01.1970'\t%Ex='01.01.1970'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%D='02/13/09'\t%F='2009-02-13'\t%x='13.02.2009'\t%Ex='13.02.2009'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else
+  check(SV("%D='01/01/70'\t%F='1970-01-01'\t%x='01/01/1970'\t%Ex='01/01/1970'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%D='02/13/09'\t%F='2009-02-13'\t%x='13/02/2009'\t%Ex='13/02/2009'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+#if defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%D='01/01/70'\t%F='1970-01-01'\t%x='1970/01/01'\t%Ex='1970/01/01'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%D='02/13/09'\t%F='2009-02-13'\t%x='2009/02/13'\t%Ex='2009/02/13'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else                                  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%D='01/01/70'\t%F='1970-01-01'\t%x='1970年01月01日'\t%Ex='昭和45年01月01日'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%D='02/13/09'\t%F='2009-02-13'\t%x='2009年02月13日'\t%Ex='平成21年02月13日'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif                                 // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_time() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt = SV(
+      "{:"
+      "%%H='%H'%t"
+      "%%OH='%OH'%t"
+      "%%I='%I'%t"
+      "%%OI='%OI'%t"
+      "%%M='%M'%t"
+      "%%OM='%OM'%t"
+      "%%S='%S'%t"
+      "%%OS='%OS'%t"
+      "%%p='%p'%t"
+      "%%R='%R'%t"
+      "%%T='%T'%t"
+      "%%r='%r'%t"
+      "%%X='%X'%t"
+      "%%EX='%EX'%t"
+      "%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV(
+      "{:L"
+      "%%H='%H'%t"
+      "%%OH='%OH'%t"
+      "%%I='%I'%t"
+      "%%OI='%OI'%t"
+      "%%M='%M'%t"
+      "%%OM='%OM'%t"
+      "%%S='%S'%t"
+      "%%OS='%OS'%t"
+      "%%p='%p'%t"
+      "%%R='%R'%t"
+      "%%T='%T'%t"
+      "%%r='%r'%t"
+      "%%X='%X'%t"
+      "%%EX='%EX'%t"
+      "%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%H='00'\t"
+           "%OH='00'\t"
+           "%I='12'\t"
+           "%OI='12'\t"
+           "%M='00'\t"
+           "%OM='00'\t"
+           "%S='00'\t"
+           "%OS='00'\t"
+           "%p='AM'\t"
+           "%R='00:00'\t"
+           "%T='00:00:00'\t"
+           "%r='12:00:00 AM'\t"
+           "%X='00:00:00'\t"
+           "%EX='00:00:00'\t"
+           "\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%H='23'\t"
+           "%OH='23'\t"
+           "%I='11'\t"
+           "%OI='11'\t"
+           "%M='31'\t"
+           "%OM='31'\t"
+           "%S='30.123'\t"
+           "%OS='30.123'\t"
+           "%p='PM'\t"
+           "%R='23:31'\t"
+           "%T='23:31:30.123'\t"
+           "%r='11:31:30 PM'\t"
+           "%X='23:31:30'\t"
+           "%EX='23:31:30'\t"
+           "\n"),
+        fmt,
+        std::chrono::sys_time<std::chrono::milliseconds>(
+            1'234'567'890'123ms)); // 23:31:30 UTC on Friday, 13 February 2009
+  // Use the global locale (fr_FR)
+  check(SV("%H='00'\t"
+           "%OH='00'\t"
+           "%I='12'\t"
+           "%OI='12'\t"
+           "%M='00'\t"
+           "%OM='00'\t"
+           "%S='00'\t"
+           "%OS='00'\t"
+#if defined(_AIX)
+           "%p='AM'\t"
+#else
+           "%p=''\t"
+#endif
+           "%R='00:00'\t"
+           "%T='00:00:00'\t"
+#ifdef _WIN32
+           "%r='00:00:00'\t"
+#elif defined(_AIX)
+           "%r='12:00:00 AM'\t"
+#elif defined(__APPLE__)
+           "%r=''\t"
+#else
+           "%r='12:00:00 '\t"
+#endif
+           "%X='00:00:00'\t"
+           "%EX='00:00:00'\t"
+           "\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%H='23'\t"
+           "%OH='23'\t"
+           "%I='11'\t"
+           "%OI='11'\t"
+           "%M='31'\t"
+           "%OM='31'\t"
+           "%S='30,123'\t"
+           "%OS='30,123'\t"
+#if defined(_AIX)
+           "%p='PM'\t"
+#else
+           "%p=''\t"
+#endif
+           "%R='23:31'\t"
+           "%T='23:31:30,123'\t"
+#ifdef _WIN32
+           "%r='23:31:30'\t"
+#elif defined(_AIX)
+           "%r='11:31:30 PM'\t"
+#elif defined(__APPLE__)
+           "%r=''\t"
+#else
+           "%r='11:31:30 '\t"
+#endif
+           "%X='23:31:30'\t"
+           "%EX='23:31:30'\t"
+           "\n"),
+        lfmt,
+        std::chrono::sys_time<std::chrono::milliseconds>(
+            1'234'567'890'123ms)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.a
+#if defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%H='00'\t"
+           "%OH='00'\t"
+           "%I='12'\t"
+           "%OI='12'\t"
+           "%M='00'\t"
+           "%OM='00'\t"
+           "%S='00'\t"
+           "%OS='00'\t"
+#  if defined(__APPLE__)
+           "%p='AM'\t"
+#  else
+           "%p='午前'\t"
+#  endif
+           "%R='00:00'\t"
+           "%T='00:00:00'\t"
+#  if defined(__APPLE__)
+           "%r='12:00:00 AM'\t"
+           "%X='00時00分00秒'\t"
+           "%EX='00時00分00秒'\t"
+#  else
+           "%r='午前12:00:00'\t"
+           "%X='00:00:00'\t"
+           "%EX='00:00:00'\t"
+#  endif
+           "\n"),
+        lfmt,
+        std::chrono::hh_mm_ss(0s));
+
+  check(loc,
+        SV("%H='23'\t"
+           "%OH='23'\t"
+           "%I='11'\t"
+           "%OI='11'\t"
+           "%M='31'\t"
+           "%OM='31'\t"
+           "%S='30.123'\t"
+           "%OS='30.123'\t"
+#  if defined(__APPLE__)
+           "%p='PM'\t"
+#  else
+           "%p='午後'\t"
+#  endif
+           "%R='23:31'\t"
+           "%T='23:31:30.123'\t"
+#  if defined(__APPLE__)
+           "%r='11:31:30 PM'\t"
+           "%X='23時31分30秒'\t"
+           "%EX='23時31分30秒'\t"
+#  else
+           "%r='午後11:31:30'\t"
+           "%X='23:31:30'\t"
+           "%EX='23:31:30'\t"
+#  endif
+           "\n"),
+        lfmt,
+        std::chrono::hh_mm_ss(23h + 31min + 30s + 123ms));
+#else  // defined(__APPLE__) || defined(_AIX)
+  check(loc,
+        SV("%H='00'\t"
+           "%OH='〇'\t"
+           "%I='12'\t"
+           "%OI='十二'\t"
+           "%M='00'\t"
+           "%OM='〇'\t"
+           "%S='00'\t"
+           "%OS='〇'\t"
+           "%p='午前'\t"
+           "%R='00:00'\t"
+           "%T='00:00:00'\t"
+           "%r='午前12時00分00秒'\t"
+           "%X='00時00分00秒'\t"
+           "%EX='00時00分00秒'\t"
+           "\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%H='23'\t"
+           "%OH='二十三'\t"
+           "%I='11'\t"
+           "%OI='十一'\t"
+           "%M='31'\t"
+           "%OM='三十一'\t"
+           "%S='30.123'\t"
+           "%OS='三十.123'\t"
+           "%p='午後'\t"
+           "%R='23:31'\t"
+           "%T='23:31:30.123'\t"
+           "%r='午後11時31分30秒'\t"
+           "%X='23時31分30秒'\t"
+           "%EX='23時31分30秒'\t"
+           "\n"),
+        lfmt,
+        std::chrono::sys_time<std::chrono::milliseconds>(
+            1'234'567'890'123ms)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif // defined(__APPLE__) || defined(_AIX)
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_date_time() {
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%c='%c'%t%%Ec='%Ec'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%c='%c'%t%%Ec='%Ec'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+  // Non localized output using C-locale
+  check(SV("%c='Thu Jan  1 00:00:00 1970'\t%Ec='Thu Jan  1 00:00:00 1970'\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(SV("%c='Fri Feb 13 23:31:30 2009'\t%Ec='Fri Feb 13 23:31:30 2009'\n"),
+        fmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use the global locale (fr_FR)
+  check(
+// https://sourceware.org/bugzilla/show_bug.cgi?id=24054
+#if defined(__GLIBC__) && __GLIBC__ <= 2 && __GLIBC_MINOR__ < 29
+      SV("%c='jeu. 01 janv. 1970 00:00:00 GMT'\t%Ec='jeu. 01 janv. 1970 00:00:00 GMT'\n"),
+#elif defined(_AIX)
+      SV("%c=' 1 janvier 1970 à 00:00:00 UTC'\t%Ec=' 1 janvier 1970 à 00:00:00 UTC'\n"),
+#elif defined(__APPLE__)
+      SV("%c='Jeu  1 jan 00:00:00 1970'\t%Ec='Jeu  1 jan 00:00:00 1970'\n"),
+#else
+      SV("%c='jeu. 01 janv. 1970 00:00:00'\t%Ec='jeu. 01 janv. 1970 00:00:00'\n"),
+#endif
+      lfmt,
+      file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(
+// https://sourceware.org/bugzilla/show_bug.cgi?id=24054
+#if defined(__GLIBC__) && __GLIBC__ <= 2 && __GLIBC_MINOR__ < 29
+      SV("%c='ven. 13 févr. 2009 23:31:30 GMT'\t%Ec='ven. 13 févr. 2009 23:31:30 GMT'\n"),
+#elif defined(_AIX)
+      SV("%c='13 février 2009 à 23:31:30 UTC'\t%Ec='13 février 2009 à 23:31:30 UTC'\n"),
+#elif defined(__APPLE__)
+      SV("%c='Ven 13 fév 23:31:30 2009'\t%Ec='Ven 13 fév 23:31:30 2009'\n"),
+#else
+      SV("%c='ven. 13 févr. 2009 23:31:30'\t%Ec='ven. 13 févr. 2009 23:31:30'\n"),
+#endif
+      lfmt,
+      file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.a
+#if defined(__APPLE__)
+  check(loc,
+        SV("%c='木  1/ 1 00:00:00 1970'\t%Ec='木  1/ 1 00:00:00 1970'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+  check(loc,
+        SV("%c='金  2/13 23:31:30 2009'\t%Ec='金  2/13 23:31:30 2009'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#elif defined(_AIX)                    // __APPLE__
+  check(loc,
+        SV("%c='1970年01月 1日 00:00:00 UTC'\t%Ec='1970年01月 1日 00:00:00 UTC'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+  check(loc,
+        SV("%c='2009年02月13日 23:31:30 UTC'\t%Ec='2009年02月13日 23:31:30 UTC'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else                                  // __APPLE__
+  check(loc,
+        SV("%c='1970年01月01日 00時00分00秒'\t%Ec='昭和45年01月01日 00時00分00秒'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%c='2009年02月13日 23時31分30秒'\t%Ec='平成21年02月13日 23時31分30秒'\n"),
+        lfmt,
+        file_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif                                 // __APPLE__
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_time_zone() {
+// The Apple CI gives %z='-0700'	%Ez='-0700'	%Oz='-0700'	%Z='UTC'
+// -0700 looks like the local time where the CI happens to recide, therefore
+// omit this test on Apple.
+#if !defined(__APPLE__)
+  using namespace std::literals::chrono_literals;
+
+  constexpr std::basic_string_view<CharT> fmt  = SV("{:%%z='%z'%t%%Ez='%Ez'%t%%Oz='%Oz'%t%%Z='%Z'%n}");
+  constexpr std::basic_string_view<CharT> lfmt = SV("{:L%%z='%z'%t%%Ez='%Ez'%t%%Oz='%Oz'%t%%Z='%Z'%n}");
+
+  const std::locale loc(LOCALE_ja_JP_UTF_8);
+  std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
+
+#  if defined(_AIX)
+  // Non localized output using C-locale
+  check(SV("%z='UTC'\t%Ez='UTC'\t%Oz='UTC'\t%Z='UTC'\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  // Use the global locale (fr_FR)
+  check(SV("%z='UTC'\t%Ez='UTC'\t%Oz='UTC'\t%Z='UTC'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.a
+  check(loc,
+        SV("%z='UTC'\t%Ez='UTC'\t%Oz='UTC'\t%Z='UTC'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+#  else                    // defined(_AIX)
+  // Non localized output using C-locale
+  check(SV("%z='+0000'\t%Ez='+0000'\t%Oz='+0000'\t%Z='UTC'\n"),
+        fmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  // Use the global locale (fr_FR)
+  check(SV("%z='+0000'\t%Ez='+0000'\t%Oz='+0000'\t%Z='UTC'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.a
+  check(loc,
+        SV("%z='+0000'\t%Ez='+0000'\t%Oz='+〇'\t%Z='UTC'\n"),
+        lfmt,
+        file_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+#  endif                   // defined(_AIX)
+  std::locale::global(std::locale::classic());
+#endif                     // !defined(__APPLE__)
+}
+
+template <class CharT>
+static void test_valid_values() {
+  test_valid_values_year<CharT>();
+  test_valid_values_month<CharT>();
+  test_valid_values_day<CharT>();
+  test_valid_values_weekday<CharT>();
+  test_valid_values_day_of_year<CharT>();
+  test_valid_values_week<CharT>();
+  test_valid_values_iso_8601_week<CharT>();
+  test_valid_values_date<CharT>();
+  test_valid_values_time<CharT>();
+  test_valid_values_date_time<CharT>();
+  test_valid_values_time_zone<CharT>();
+}
+
+template <class CharT>
+static void test() {
+  using namespace std::literals::chrono_literals;
+
+  test_no_chrono_specs<CharT>();
+  test_valid_values<CharT>();
+
+  check_invalid_types<CharT>(
+      {SV("a"),  SV("A"),  SV("b"),  SV("B"),  SV("c"),  SV("C"),  SV("d"),  SV("D"),  SV("e"),  SV("F"),  SV("g"),
+       SV("G"),  SV("h"),  SV("H"),  SV("I"),  SV("j"),  SV("m"),  SV("M"),  SV("p"),  SV("r"),  SV("R"),  SV("S"),
+       SV("T"),  SV("u"),  SV("U"),  SV("V"),  SV("w"),  SV("W"),  SV("x"),  SV("X"),  SV("y"),  SV("Y"),  SV("z"),
+       SV("Z"),  SV("Ec"), SV("EC"), SV("Ex"), SV("EX"), SV("Ey"), SV("EY"), SV("Ez"), SV("Od"), SV("Oe"), SV("OH"),
+       SV("OI"), SV("Om"), SV("OM"), SV("OS"), SV("Ou"), SV("OU"), SV("OV"), SV("Ow"), SV("OW"), SV("Oy"), SV("Oz")},
+      file_seconds(0s));
+
+  check_exception("Expected '%' or '}' in the chrono format-string", SV("{:A"), file_seconds(0s));
+  check_exception("The chrono-specs contains a '{'", SV("{:%%{"), file_seconds(0s));
+  check_exception("End of input while parsing the modifier chrono conversion-spec", SV("{:%"), file_seconds(0s));
+  check_exception("End of input while parsing the modifier E", SV("{:%E"), file_seconds(0s));
+  check_exception("End of input while parsing the modifier O", SV("{:%O"), file_seconds(0s));
+
+  // Precision not allowed
+  check_exception("Expected '%' or '}' in the chrono format-string", SV("{:.3}"), file_seconds(0s));
+}
+
+int main(int, char**) {
+  test<char>();
+
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  test<wchar_t>();
+#endif
+
+  return 0;
+}
diff --git a/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp b/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp
index 6957c7b..d10fcf3 100644
--- a/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formattable/concept.formattable.compile.pass.cpp
@@ -140,7 +140,7 @@ void test_P1361() {
   //assert_is_formattable<std::chrono::utc_time<std::chrono::microseconds>, CharT>();
   //assert_is_formattable<std::chrono::tai_time<std::chrono::microseconds>, CharT>();
   //assert_is_formattable<std::chrono::gps_time<std::chrono::microseconds>, CharT>();
-  assert_is_not_formattable<std::chrono::file_time<std::chrono::microseconds>, CharT>();
+  assert_is_formattable<std::chrono::file_time<std::chrono::microseconds>, CharT>();
   assert_is_not_formattable<std::chrono::local_time<std::chrono::microseconds>, CharT>();
 
   assert_is_formattable<std::chrono::day, CharT>();