[llvm-branch-commits] [libcxx] [libc++][chrono] implements UTC clock. (PR #90393)

Matt Stephanson via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Tue Apr 30 09:15:53 PDT 2024


================
@@ -0,0 +1,1004 @@
+//===----------------------------------------------------------------------===//
+// 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-filesystem, no-localization, no-tzdb
+// UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
+
+// TODO FMT This test should not require std::to_chars(floating-point)
+// XFAIL: availability-fp_to_chars-missing
+
+// XFAIL: libcpp-has-no-incomplete-tzdb
+// XFAIL: availability-tzdb-missing
+
+// REQUIRES: locale.fr_FR.UTF-8
+// REQUIRES: locale.ja_JP.UTF-8
+
+// <chrono>
+
+// template<class Duration, class charT>
+//   struct formatter<chrono::utc_time<Duration>, 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"
+
+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
+
+  // [time.syn]
+  //   using nanoseconds  = duration<signed integer type of at least 64 bits, nano>;
+  //   using microseconds = duration<signed integer type of at least 55 bits, micro>;
+  //   using milliseconds = duration<signed integer type of at least 45 bits, milli>;
+  //   using seconds      = duration<signed integer type of at least 35 bits>;
+  //   using minutes      = duration<signed integer type of at least 29 bits, ratio<  60>>;
+  //   using hours        = duration<signed integer type of at least 23 bits, ratio<3600>>;
+  check(SV("1425-08-04 22:06:56"), SV("{}"), std::chrono::utc_seconds(-17'179'869'184s)); // Minimum value for 35 bits.
+  check(SV("1901-12-13 20:45:52"), SV("{}"), std::chrono::utc_seconds(-2'147'483'648s));
+
+  check(SV("1969-12-31 00:00:00"), SV("{}"), std::chrono::utc_seconds(-24h));
+  check(SV("1969-12-31 06:00:00"), SV("{}"), std::chrono::utc_seconds(-18h));
+  check(SV("1969-12-31 12:00:00"), SV("{}"), std::chrono::utc_seconds(-12h));
+  check(SV("1969-12-31 18:00:00"), SV("{}"), std::chrono::utc_seconds(-6h));
+  check(SV("1969-12-31 23:59:59"), SV("{}"), std::chrono::utc_seconds(-1s));
+
+  check(SV("1970-01-01 00:00:00"), SV("{}"), std::chrono::utc_seconds(0s));
+  check(SV("2000-01-01 00:00:00"), SV("{}"), std::chrono::utc_seconds(946'684'800s + 22s));
+  check(SV("2000-01-01 01:02:03"), SV("{}"), std::chrono::utc_seconds(946'688'523s + 22s));
+
+  check(SV("2038-01-19 03:14:07"), SV("{}"), std::chrono::utc_seconds(2'147'483'647s + 27s));
+  check(SV("2514-05-30 01:53:03"),
+        SV("{}"),
+        std::chrono::utc_seconds(17'179'869'183s + 27s)); // Maximum value for 35 bits.
+
+  check(SV("2000-01-01 01:02:03.123"),
+        SV("{}"),
+        std::chrono::utc_time<std::chrono::milliseconds>(946'688'523'123ms + 22s));
+
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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) || defined(__FreeBSD__)
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)||defined(__FreeBSD__)
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif // defined(_WIN32) || defined(__APPLE__) || defined(_AIX)||defined(__FreeBSD__)
+
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#elif defined(__FreeBSD__)                         // _WIN32
+  check(loc,
+        SV("%b=' 1月'\t%h=' 1月'\t%B='1月'\t%m='01'\t%Om='01'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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) || defined(__FreeBSD__)
+  check(loc,
+        SV("%d='01'\t%Od='01'\t%e=' 1'\t%Oe=' 1'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+  check(loc,
+        SV("%d='01'\t%Od='一'\t%e=' 1'\t%Oe='一'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+#endif // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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) || defined(__FreeBSD__)
+  check(loc,
+        SV("%a='木'\t%A='木曜日'\t%u='4'\t%Ou='4'\t%w='4'\t%Ow='4'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(4'294'967'295s)); // 06:28:15 UTC on Sunday, 7 February 2106
+#else  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+  check(loc,
+        SV("%a='木'\t%A='木曜日'\t%u='4'\t%Ou='四'\t%w='4'\t%Ow='四'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(4'294'967'295s)); // 06:28:15 UTC on Sunday, 7 February 2106
+#endif // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+
+  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, std::chrono::utc_seconds(0s));             // 00:00:00 UTC Thursday, 1 January 1970
+  check(SV("%j='138'\n"), fmt, std::chrono::utc_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, std::chrono::utc_seconds(0s));             // 00:00:00 UTC Thursday, 1 January 1970
+  check(SV("%j='138'\n"), lfmt, std::chrono::utc_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, std::chrono::utc_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(
+      loc, SV("%j='138'\n"), lfmt, std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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) || defined(__FreeBSD__)
+  check(loc,
+        SV("%U='00'\t%OU='00'\t%W='00'\t%OW='00'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#else  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+  check(loc,
+        SV("%U='00'\t%OU='〇'\t%W='00'\t%OW='〇'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(2'000'000'000s)); // 03:33:20 UTC on Wednesday, 18 May 2033
+#endif // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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) || defined(__FreeBSD__)
+  check(loc,
+        SV("%g='70'\t%G='1970'\t%V='01'\t%OV='01'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+  check(loc,
+        SV("%g='70'\t%G='1970'\t%V='01'\t%OV='一'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use the global locale (fr_FR)
+#if defined(__APPLE__) || defined(__FreeBSD__)
+  check(SV("%D='01/01/70'\t%F='1970-01-01'\t%x='01.01.1970'\t%Ex='01.01.1970'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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,
+        std::chrono::utc_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) || defined(__FreeBSD__)
+  check(loc,
+        SV("%D='01/01/70'\t%F='1970-01-01'\t%x='1970/01/01'\t%Ex='1970/01/01'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else  // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif // defined(_WIN32) || defined(__APPLE__) || defined(_AIX) || defined(__FreeBSD__)
+
+  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,
+        std::chrono::utc_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::utc_time<std::chrono::milliseconds>(
+            1'234'567'890'123ms + 24s)); // 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__) || defined(__FreeBSD__)
+           "%r=''\t"
+#else
+           "%r='12:00:00 '\t"
+#endif
+           "%X='00:00:00'\t"
+           "%EX='00:00:00'\t"
+           "\n"),
+        lfmt,
+        std::chrono::utc_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__) || defined(__FreeBSD__)
+           "%r=''\t"
+#else
+           "%r='11:31:30 '\t"
+#endif
+           "%X='23:31:30'\t"
+           "%EX='23:31:30'\t"
+           "\n"),
+        lfmt,
+        std::chrono::utc_time<std::chrono::milliseconds>(
+            1'234'567'890'123ms + 24s)); // 23:31:30 UTC on Friday, 13 February 2009
+
+  // Use supplied locale (ja_JP). This locale has a different alternate.
+#if defined(__APPLE__) || defined(_AIX) || defined(_WIN32) || defined(__FreeBSD__)
+  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__) || defined(__FreeBSD__)
+#    if defined(__APPLE__)
+           "%r='12:00:00 AM'\t"
+#    else
+           "%r='12:00:00 午前'\t"
+#    endif
+           "%X='00時00分00秒'\t"
+           "%EX='00時00分00秒'\t"
+#  elif defined(_WIN32)
+           "%r='0:00:00'\t"
+           "%X='0:00:00'\t"
+           "%EX='0:00:00'\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__) || defined(__FreeBSD__)
+#    if defined(__APPLE__)
+           "%r='11:31:30 PM'\t"
+#    else
+           "%r='11:31:30 午後'\t"
+#    endif
+           "%X='23時31分30秒'\t"
+           "%EX='23時31分30秒'\t"
+#  elif defined(_WIN32)
+           "%r='23:31:30'\t"
+           "%X='23:31:30'\t"
+           "%EX='23:31:30'\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) || defined(_WIN32) || defined(__FreeBSD__)
+  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,
+        std::chrono::utc_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::utc_time<std::chrono::milliseconds>(
+            1'234'567'890'123ms + 24s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif // defined(__APPLE__) || defined(_AIX) || defined(_WIN32) || defined(__FreeBSD__)
+
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s + 24s)); // 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(__powerpc__) && defined(__linux__)
+      SV("%c='jeu. 01 janv. 1970 00:00:00 UTC'\t%Ec='jeu. 01 janv. 1970 00:00:00 UTC'\n"),
+#elif 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"),
+#elif defined(_WIN32)
+      SV("%c='01/01/1970 00:00:00'\t%Ec='01/01/1970 00:00:00'\n"),
+#elif defined(__FreeBSD__)
+      SV("%c='jeu.  1 janv. 00:00:00 1970'\t%Ec='jeu.  1 janv. 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,
+      std::chrono::utc_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(
+// https://sourceware.org/bugzilla/show_bug.cgi?id=24054
+#if defined(__powerpc__) && defined(__linux__)
+      SV("%c='ven. 13 févr. 2009 23:31:30 UTC'\t%Ec='ven. 13 févr. 2009 23:31:30 UTC'\n"),
+#elif 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"),
+#elif defined(_WIN32)
+      SV("%c='13/02/2009 23:31:30'\t%Ec='13/02/2009 23:31:30'\n"),
+#elif defined(__FreeBSD__)
+      SV("%c='ven. 13 févr. 23:31:30 2009'\t%Ec='ven. 13 févr. 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,
+      std::chrono::utc_seconds(1'234'567'890s + 24s)); // 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(__FreeBSD__)
+  check(loc,
+        SV("%c='木  1/ 1 00:00:00 1970'\t%Ec='木  1/ 1 00:00:00 1970'\n"),
+        lfmt,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#elif defined(_AIX)                                // defined(__APPLE__)|| defined(__FreeBSD__)
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#elif defined(_WIN32)                              // defined(__APPLE__)|| defined(__FreeBSD__)
+  check(loc,
+        SV("%c='1970/01/01 0:00:00'\t%Ec='1970/01/01 0:00:00'\n"),
+        lfmt,
+        std::chrono::utc_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+  check(loc,
+        SV("%c='2009/02/13 23:31:30'\t%Ec='2009/02/13 23:31:30'\n"),
+        lfmt,
+        std::chrono::utc_seconds(1'234'567'890s)); // 23:31:30 UTC on Friday, 13 February 2009
+#else                                              // defined(__APPLE__)|| defined(__FreeBSD__)
+  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,
+        std::chrono::utc_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,
+        std::chrono::utc_seconds(1'234'567'890s + 24s)); // 23:31:30 UTC on Friday, 13 February 2009
+#endif                                             // defined(__APPLE__)|| defined(__FreeBSD__)
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_valid_values_time_zone() {
+  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));
+
+  // Non localized output using C-locale
+  check(SV("%z='+0000'\t%Ez='+00:00'\t%Oz='+00:00'\t%Z='UTC'\n"),
+        fmt,
+        std::chrono::utc_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  // Use the global locale (fr_FR)
+  check(SV("%z='+0000'\t%Ez='+00:00'\t%Oz='+00:00'\t%Z='UTC'\n"),
+        lfmt,
+        std::chrono::utc_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  // Use supplied locale (ja_JP).
+  check(loc,
+        SV("%z='+0000'\t%Ez='+00:00'\t%Oz='+00:00'\t%Z='UTC'\n"),
+        lfmt,
+        std::chrono::utc_seconds(0s)); // 00:00:00 UTC Thursday, 1 January 1970
+
+  std::locale::global(std::locale::classic());
+}
+
+template <class CharT>
+static void test_utc_transitions() {
----------------
MattStephanson wrote:

If you can customize the leap second db like in some of the other tests, it might be useful to verify that a negative leap second has the correct behavior, i.e., "23:59:58" is followed by "00:00:00".

https://github.com/llvm/llvm-project/pull/90393


More information about the llvm-branch-commits mailing list