[libcxx-commits] [libcxx] [libc++][TZDB] Implements zoned_time formatters. (PR #98347)

Mark de Wever via libcxx-commits libcxx-commits at lists.llvm.org
Wed Jul 17 09:43:57 PDT 2024


https://github.com/mordante updated https://github.com/llvm/llvm-project/pull/98347

>From fb6e4ac82295032e3d28b9a93e92a536c9992f6c Mon Sep 17 00:00:00 2001
From: Mark de Wever <koraq at xs4all.nl>
Date: Wed, 17 Apr 2024 21:00:22 +0200
Subject: [PATCH 1/2] [libc++][TZDB] Implements zoned_time formatters.

Implements parts of:
- P0355 Extending to chrono Calendars and Time Zones
- P1361 Integration of chrono with text formatting
- P2372 Fixing locale handling in chrono formatters
---
 libcxx/docs/Status/FormatPaper.csv            |   4 +-
 libcxx/include/__chrono/convert_to_tm.h       |   8 +
 libcxx/include/__chrono/formatter.h           |  57 +
 libcxx/include/__chrono/ostream.h             |  11 +-
 libcxx/include/chrono                         |   7 +
 .../time.syn/formatter.zoned_time.pass.cpp    | 974 ++++++++++++++++++
 .../test_offset_time_zone.h                   |  19 +
 .../ostream.pass.cpp                          | 348 +++++++
 8 files changed, 1425 insertions(+), 3 deletions(-)
 create mode 100644 libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp
 create mode 100644 libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp

diff --git a/libcxx/docs/Status/FormatPaper.csv b/libcxx/docs/Status/FormatPaper.csv
index f29f1f7ca7487..fb96b1fff30ad 100644
--- a/libcxx/docs/Status/FormatPaper.csv
+++ b/libcxx/docs/Status/FormatPaper.csv
@@ -7,7 +7,7 @@ Section,Description,Dependencies,Assignee,Status,First released version
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::gps_time<Duration>``",A ``<chrono>`` implementation,Mark de Wever,,,
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::file_time<Duration>``",,Mark de Wever,|Complete|,17.0
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::local_time<Duration>``",,Mark de Wever,|Complete|,17.0
-`[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::local-time-format-t<Duration>``",A ``<chrono>`` implementation,Mark de Wever,,,
+`[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::local-time-format-t<Duration>``",,,|Nothing To Do|,
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::day``",,Mark de Wever,|Complete|,16.0
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::month``",,Mark de Wever,|Complete|,16.0
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::year``",,Mark de Wever,|Complete|,16.0
@@ -26,7 +26,7 @@ Section,Description,Dependencies,Assignee,Status,First released version
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::hh_mm_ss<duration<Rep, Period>>``",,Mark de Wever,|Complete|,17.0
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::sys_info``",,Mark de Wever,|Complete|,19.0
 `[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::local_info``",,Mark de Wever,|Complete|,19.0
-`[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::zoned_time<Duration, TimeZonePtr>``",A ``<chrono>`` implementation,Mark de Wever,,
+`[time.syn] <https://wg21.link/time.syn>`_,"Formatter ``chrono::zoned_time<Duration, TimeZonePtr>``",,Mark de Wever,|Complete|,19.0
 
 "`P2693R1 <https://wg21.link/P2693R1>`__","Formatting ``thread::id`` and ``stacktrace``"
 `[thread.thread.id] <https://wg21.link/thread.thread.id>`_,"Formatting ``thread::id``",,Mark de Wever,|Complete|,17.0
diff --git a/libcxx/include/__chrono/convert_to_tm.h b/libcxx/include/__chrono/convert_to_tm.h
index 881a4970822d8..8f64b97f4fa03 100644
--- a/libcxx/include/__chrono/convert_to_tm.h
+++ b/libcxx/include/__chrono/convert_to_tm.h
@@ -29,11 +29,13 @@
 #include <__chrono/year_month.h>
 #include <__chrono/year_month_day.h>
 #include <__chrono/year_month_weekday.h>
+#include <__chrono/zoned_time.h>
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__format/format_error.h>
 #include <__memory/addressof.h>
 #include <__type_traits/is_convertible.h>
+#include <__type_traits/is_specialization.h>
 #include <cstdint>
 #include <ctime>
 #include <limits>
@@ -178,6 +180,12 @@ _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const _ChronoT& __value) {
     // Has no time information.
   } else if constexpr (same_as<_ChronoT, chrono::local_info>) {
     // Has no time information.
+#  endif
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+  } else if constexpr (__is_specialization_v<_ChronoT, chrono::zoned_time>) {
+    return std::__convert_to_tm<_Tm>(
+        chrono::sys_time<typename _ChronoT::duration>{__value.get_local_time().time_since_epoch()});
 #  endif
   } else
     static_assert(sizeof(_ChronoT) == 0, "Add the missing type specialization");
diff --git a/libcxx/include/__chrono/formatter.h b/libcxx/include/__chrono/formatter.h
index e9b81c3de8a70..161e5433723a2 100644
--- a/libcxx/include/__chrono/formatter.h
+++ b/libcxx/include/__chrono/formatter.h
@@ -33,6 +33,7 @@
 #include <__chrono/year_month.h>
 #include <__chrono/year_month_day.h>
 #include <__chrono/year_month_weekday.h>
+#include <__chrono/zoned_time.h>
 #include <__concepts/arithmetic.h>
 #include <__concepts/same_as.h>
 #include <__config>
@@ -44,6 +45,7 @@
 #include <__format/parser_std_format_spec.h>
 #include <__format/write_escaped.h>
 #include <__memory/addressof.h>
+#include <__type_traits/is_specialization.h>
 #include <cmath>
 #include <ctime>
 #include <sstream>
@@ -136,10 +138,24 @@ __format_sub_seconds(basic_stringstream<_CharT>& __sstr, const chrono::hh_mm_ss<
                    __value.fractional_width);
 }
 
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+template <class _CharT, class _Duration, class _TimeZonePtr>
+_LIBCPP_HIDE_FROM_ABI void
+__format_sub_seconds(basic_stringstream<_CharT>& __sstr, const chrono::zoned_time<_Duration, _TimeZonePtr>& __value) {
+  __formatter::__format_sub_seconds(__sstr, __value.get_local_time().time_since_epoch());
+}
+#  endif
+
 template <class _Tp>
 consteval bool __use_fraction() {
   if constexpr (__is_time_point<_Tp>)
     return chrono::hh_mm_ss<typename _Tp::duration>::fractional_width;
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+  else if constexpr (__is_specialization_v<_Tp, chrono::zoned_time>)
+    return chrono::hh_mm_ss<typename _Tp::duration>::fractional_width;
+#  endif
   else if constexpr (chrono::__is_duration<_Tp>::value)
     return chrono::hh_mm_ss<_Tp>::fractional_width;
   else if constexpr (__is_hh_mm_ss<_Tp>)
@@ -211,6 +227,11 @@ _LIBCPP_HIDE_FROM_ABI __time_zone __convert_to_time_zone([[maybe_unused]] const
 #  if !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
   if constexpr (same_as<_Tp, chrono::sys_info>)
     return {__value.abbrev, __value.offset};
+#    if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                          \
+        !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+  else if constexpr (__is_specialization_v<_Tp, chrono::zoned_time>)
+    return __formatter::__convert_to_time_zone(__value.get_info());
+#    endif
   else
 #  endif
     return {"UTC", chrono::seconds{0}};
@@ -425,6 +446,11 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool __weekday_ok(const _Tp& __value) {
     return true;
   else if constexpr (same_as<_Tp, chrono::local_info>)
     return true;
+#  endif
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+  else if constexpr (__is_specialization_v<_Tp, chrono::zoned_time>)
+    return true;
 #  endif
   else
     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
@@ -471,6 +497,11 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool __weekday_name_ok(const _Tp& __value) {
     return true;
   else if constexpr (same_as<_Tp, chrono::local_info>)
     return true;
+#  endif
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+  else if constexpr (__is_specialization_v<_Tp, chrono::zoned_time>)
+    return true;
 #  endif
   else
     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
@@ -517,6 +548,11 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool __date_ok(const _Tp& __value) {
     return true;
   else if constexpr (same_as<_Tp, chrono::local_info>)
     return true;
+#  endif
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+  else if constexpr (__is_specialization_v<_Tp, chrono::zoned_time>)
+    return true;
 #  endif
   else
     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
@@ -563,6 +599,11 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool __month_name_ok(const _Tp& __value) {
     return true;
   else if constexpr (same_as<_Tp, chrono::local_info>)
     return true;
+#  endif
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+  else if constexpr (__is_specialization_v<_Tp, chrono::zoned_time>)
+    return true;
 #  endif
   else
     static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
@@ -917,6 +958,22 @@ struct formatter<chrono::local_info, _CharT> : public __formatter_chrono<_CharT>
   }
 };
 #  endif // !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+// Note due to how libc++'s formatters are implemented there is no need to add
+// the exposition only local-time-format-t abstraction.
+template <class _Duration, class _TimeZonePtr, __fmt_char_type _CharT>
+struct formatter< chrono::zoned_time<_Duration, _TimeZonePtr>, _CharT> : public __formatter_chrono<_CharT> {
+public:
+  using _Base = __formatter_chrono<_CharT>;
+
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
+    return _Base::__parse(__ctx, __format_spec::__fields_chrono, __format_spec::__flags::__clock);
+  }
+};
+#  endif // !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&
+         // !defined(_LIBCPP_HAS_NO_LOCALIZATION)
 
 #endif // if _LIBCPP_STD_VER >= 20
 
diff --git a/libcxx/include/__chrono/ostream.h b/libcxx/include/__chrono/ostream.h
index bb0341bc3ec63..af1fdc3d39b28 100644
--- a/libcxx/include/__chrono/ostream.h
+++ b/libcxx/include/__chrono/ostream.h
@@ -27,6 +27,7 @@
 #include <__chrono/year_month.h>
 #include <__chrono/year_month_day.h>
 #include <__chrono/year_month_weekday.h>
+#include <__chrono/zoned_time.h>
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__format/format_functions.h>
@@ -301,9 +302,17 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, const local_info& __info) {
   return __os << std::format(
              _LIBCPP_STATICALLY_WIDEN(_CharT, "{}: {{{}, {}}}"), __result(), __info.first, __info.second);
 }
-
 #  endif // !defined(_LIBCPP_HAS_NO_EXPERIMENTAL_TZDB)
 
+#  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
+      !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+template <class _CharT, class _Traits, class _Duration, class _TimeZonePtr>
+_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits>& __os, const zoned_time<_Duration, _TimeZonePtr>& __tp) {
+  return __os << std::format(__os.getloc(), _LIBCPP_STATICALLY_WIDEN(_CharT, "{:L%F %T %Z}"), __tp);
+}
+#  endif
+
 } // namespace chrono
 
 #endif // if _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/chrono b/libcxx/include/chrono
index 7f25c76fda542..990c415ec2e97 100644
--- a/libcxx/include/chrono
+++ b/libcxx/include/chrono
@@ -799,6 +799,11 @@ template<class Duration1, class Duration2, class TimeZonePtr>
   bool operator==(const zoned_time<Duration1, TimeZonePtr>& x,
                   const zoned_time<Duration2, TimeZonePtr>& y);
 
+template<class charT, class traits, class Duration, class TimeZonePtr>           // C++20
+  basic_ostream<charT, traits>&
+    operator<<(basic_ostream<charT, traits>& os,
+               const zoned_time<Duration, TimeZonePtr>& t);
+
 // [time.zone.leap], leap second support
 class leap_second {                                                              // C++20
 public:
@@ -881,6 +886,8 @@ namespace std {
     struct formatter<chrono::hh_mm_ss<duration<Rep, Period>>, charT>;             // C++20
   template<class charT> struct formatter<chrono::sys_info, charT>;                // C++20
   template<class charT> struct formatter<chrono::local_info, charT>;              // C++20
+  template<class Duration, class TimeZonePtr, class charT>                        // C++20
+    struct formatter<chrono::zoned_time<Duration, TimeZonePtr>, charT>;
 } // namespace std
 
 namespace chrono {
diff --git a/libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp b/libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp
new file mode 100644
index 0000000000000..98d14cbfa9005
--- /dev/null
+++ b/libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp
@@ -0,0 +1,974 @@
+//===----------------------------------------------------------------------===//
+// 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
+
+// TODO FMT This test should not require std::to_chars(floating-point)
+// XFAIL: availability-fp_to_chars-missing
+
+// XFAIL: libcpp-has-no-experimental-tzdb
+
+// REQUIRES: locale.fr_FR.UTF-8
+// REQUIRES: locale.ja_JP.UTF-8
+
+// <chrono>
+//
+// template<class Duration, class TimeZonePtr, class charT>
+// struct formatter<chrono::zoned_time<Duration, TimeZonePtr>, 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;
+
+  check(SV("1970-01-01 01:00:00.000000042 +01"),
+        SV("{}"),
+        std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::nanoseconds>{42ns}));
+  check(SV("1970-01-01 01:00:00.000042 +01"),
+        SV("{}"),
+        std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::microseconds>{42us}));
+  check(SV("1970-01-01 01:00:00.042 +01"),
+        SV("{}"),
+        std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::milliseconds>{42ms}));
+  check(SV("1970-01-01 01:00:42 +01"),
+        SV("{}"),
+        std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::seconds>{42s}));
+  check(SV("1970-02-12 01:00:00 +01"),
+        SV("{}"),
+        std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::days>{std::chrono::days{42}}));
+  check(SV("1970-10-22 01:00:00 +01"),
+        SV("{}"),
+        std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::weeks>{std::chrono::weeks{42}}));
+}
+
+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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_seconds{0s})); // 00:00:00 UTC Thursday, 1 January 1970
+  check(SV("%j='138'\n"),
+        fmt,
+        std::chrono::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_seconds{0s})); // 00:00:00 UTC Thursday, 1 January 1970
+  check(SV("%j='138'\n"),
+        lfmt,
+        std::chrono::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_seconds{0s})); // 00:00:00 UTC Thursday, 1 January 1970
+
+  check(loc,
+        SV("%j='138'\n"),
+        lfmt,
+        std::chrono::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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__) || 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::zoned_time(std::chrono::sys_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"
+#elif defined(_WIN32)
+           "%r='23:31:30 '\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) || 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::zoned_time(std::chrono::sys_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) || 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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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(__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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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__) || 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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::sys_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::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_seconds{1'234'567'890s})); // 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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_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::zoned_time(std::chrono::sys_seconds{0s})); // 00:00:00 UTC Thursday, 1 January 1970
+
+  std::locale::global(std::locale::classic());
+}
+
+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() {
+  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")},
+      std::chrono::zoned_time{});
+}
+
+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.zone/time.zone.zonedtime/test_offset_time_zone.h b/libcxx/test/std/time/time.zone/time.zone.zonedtime/test_offset_time_zone.h
index c137049bde8aa..e9262c5d95db1 100644
--- a/libcxx/test/std/time/time.zone/time.zone.zonedtime/test_offset_time_zone.h
+++ b/libcxx/test/std/time/time.zone/time.zone.zonedtime/test_offset_time_zone.h
@@ -13,6 +13,7 @@
 #include <cassert>
 #include <charconv>
 #include <chrono>
+#include <format>
 #include <string_view>
 #include <type_traits>
 
@@ -42,6 +43,8 @@ class offset_time_zone {
 
   offset_time_zone* operator->() { return this; }
 
+  const offset_time_zone* operator->() const { return this; }
+
   template <class Duration>
   std::chrono::sys_time<std::common_type_t<Duration, std::chrono::seconds>>
   to_sys(const std::chrono::local_time<Duration>& local) const {
@@ -49,6 +52,22 @@ class offset_time_zone {
         local.time_since_epoch() + offset_};
   }
 
+  template <class Duration>
+  std::chrono::local_time<std::common_type_t<Duration, std::chrono::seconds>>
+  to_local(const std::chrono::sys_time<Duration>& sys) const {
+    return std::chrono::local_time<std::common_type_t<Duration, std::chrono::seconds>>{
+        sys.time_since_epoch() - offset_};
+  }
+
+  template <class Duration>
+  std::chrono::sys_info get_info(const std::chrono::sys_time<Duration>&) const {
+    return {std::chrono::sys_seconds::min(),
+            std::chrono::sys_seconds::max(),
+            offset_,
+            std::chrono::minutes{0},
+            std::format("{:+03d}s", offset_.count())};
+  }
+
 private:
   std::chrono::seconds offset_;
 };
diff --git a/libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp
new file mode 100644
index 0000000000000..82fd2e7b9f26c
--- /dev/null
+++ b/libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp
@@ -0,0 +1,348 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// TODO FMT This test should not require std::to_chars(floating-point)
+// XFAIL: availability-fp_to_chars-missing
+
+// XFAIL: libcpp-has-no-experimental-tzdb
+
+// <chrono>
+
+// template<class charT, class traits, class Duration, class TimeZonePtr>
+// basic_ostream<charT, traits>&
+// operator<<(basic_ostream<charT, traits>& os,
+//            const zoned_time<Duration, TimeZonePtr>& t);
+
+#include <chrono>
+#include <cassert>
+#include <sstream>
+
+#include "assert_macros.h"
+#include "concat_macros.h"
+#include "make_string.h"
+#include "platform_support.h" // locale name macros
+#include "test_macros.h"
+#include "../test_offset_time_zone.h"
+
+#define SV(S) MAKE_STRING_VIEW(CharT, S)
+
+#define TEST_EQUAL(OUT, EXPECTED)                                                                                      \
+  TEST_REQUIRE(OUT == EXPECTED,                                                                                        \
+               TEST_WRITE_CONCATENATED(                                                                                \
+                   "\nExpression      ", #OUT, "\nExpected output ", EXPECTED, "\nActual output   ", OUT, '\n'));
+
+template <class CharT, class Duration, class TimeZonePtr>
+static std::basic_string<CharT> stream_c_locale(std::chrono::zoned_time<Duration, TimeZonePtr> time_point) {
+  std::basic_stringstream<CharT> sstr;
+  sstr << time_point;
+  return sstr.str();
+}
+
+template <class CharT, class Duration, class TimeZonePtr>
+static std::basic_string<CharT> stream_fr_FR_locale(std::chrono::zoned_time<Duration, TimeZonePtr> time_point) {
+  std::basic_stringstream<CharT> sstr;
+  const std::locale locale(LOCALE_fr_FR_UTF_8);
+  sstr.imbue(locale);
+  sstr << time_point;
+  return sstr.str();
+}
+
+template <class CharT, class Duration, class TimeZonePtr>
+static std::basic_string<CharT> stream_ja_JP_locale(std::chrono::zoned_time<Duration, TimeZonePtr> time_point) {
+  std::basic_stringstream<CharT> sstr;
+  const std::locale locale(LOCALE_ja_JP_UTF_8);
+  sstr.imbue(locale);
+  sstr << time_point;
+  return sstr.str();
+}
+
+template <class CharT>
+static void test_c() {
+  using namespace std::literals::chrono_literals;
+
+  { //  Different durations
+    TEST_EQUAL(stream_c_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::nanoseconds>{42ns})),
+               SV("1970-01-01 01:00:00.000000042 +01"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::microseconds>{42us})),
+               SV("1970-01-01 01:00:00.000042 +01"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::milliseconds>{42ms})),
+               SV("1970-01-01 01:00:00.042 +01"));
+
+    TEST_EQUAL(
+        stream_c_locale<CharT>(std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::seconds>{42s})),
+        SV("1970-01-01 01:00:42 +01"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Etc/GMT-1", std::chrono::sys_time<std::chrono::days>{std::chrono::days{42}})),
+               SV("1970-02-12 01:00:00 +01"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Etc/GMT-1", std::chrono::sys_time<std::chrono::weeks>{std::chrono::weeks{42}})),
+               SV("1970-10-22 01:00:00 +01"));
+  }
+
+  { // Daylight saving time switches
+    // Pick an historic date where it's well known what the time zone rules were.
+    // This makes it unlikely updates to the database change these rules.
+
+    // Z Europe/Berlin 0:53:28 - LMT 1893 Ap
+    // ...
+    // 1 DE CE%sT 1980
+    // 1 E CE%sT
+    //
+    // ...
+    // R E 1979 1995 - S lastSu 1u 0 -
+    // R E 1981 ma - Mar lastSu 1u 1 S
+
+    // Pick an historic date where it's well known what the time zone rules were.
+    // This makes it unlikely updates to the database change these rules.
+
+    // Start of daylight saving time
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::March / 30 / 1986} + 0h + 59min + 59s)),
+               SV("1986-03-30 01:59:59 CET"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::March / 30 / 1986} + 1h)),
+               SV("1986-03-30 03:00:00 CEST"));
+
+    // End of daylight saving time
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 0h + 59min + 59s)),
+               SV("1986-09-28 02:59:59 CEST"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 1h)),
+               SV("1986-09-28 02:00:00 CET"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 1h + 59min + 59s)),
+               SV("1986-09-28 02:59:59 CET"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 2h)),
+               SV("1986-09-28 03:00:00 CET"));
+  }
+
+  { // offset pointer
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{}, std::chrono::sys_seconds{})),
+               SV("1970-01-01 00:00:00 +00s"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{"42"}, std::chrono::sys_seconds{})),
+               SV("1969-12-31 23:59:18 +42s"));
+
+    TEST_EQUAL(stream_c_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{"-42"}, std::chrono::sys_seconds{})),
+               SV("1970-01-01 00:00:42 -42s"));
+  }
+}
+
+template <class CharT>
+static void test_fr_FR() {
+  using namespace std::literals::chrono_literals;
+
+  { //  Different durations
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::nanoseconds>{42ns})),
+               SV("1970-01-01 01:00:00,000000042 +01"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::microseconds>{42us})),
+               SV("1970-01-01 01:00:00,000042 +01"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::milliseconds>{42ms})),
+               SV("1970-01-01 01:00:00,042 +01"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::seconds>{42s})),
+               SV("1970-01-01 01:00:42 +01"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Etc/GMT-1", std::chrono::sys_time<std::chrono::days>{std::chrono::days{42}})),
+               SV("1970-02-12 01:00:00 +01"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Etc/GMT-1", std::chrono::sys_time<std::chrono::weeks>{std::chrono::weeks{42}})),
+               SV("1970-10-22 01:00:00 +01"));
+  }
+
+  { // Daylight saving time switches
+    // Pick an historic date where it's well known what the time zone rules were.
+    // This makes it unlikely updates to the database change these rules.
+
+    // Z Europe/Berlin 0:53:28 - LMT 1893 Ap
+    // ...
+    // 1 DE CE%sT 1980
+    // 1 E CE%sT
+    //
+    // ...
+    // R E 1979 1995 - S lastSu 1u 0 -
+    // R E 1981 ma - Mar lastSu 1u 1 S
+
+    // Pick an historic date where it's well known what the time zone rules were.
+    // This makes it unlikely updates to the database change these rules.
+
+    // Start of daylight saving time
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::March / 30 / 1986} + 0h + 59min + 59s)),
+               SV("1986-03-30 01:59:59 CET"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::March / 30 / 1986} + 1h)),
+               SV("1986-03-30 03:00:00 CEST"));
+
+    // End of daylight saving time
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 0h + 59min + 59s)),
+               SV("1986-09-28 02:59:59 CEST"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 1h)),
+               SV("1986-09-28 02:00:00 CET"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 1h + 59min + 59s)),
+               SV("1986-09-28 02:59:59 CET"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 2h)),
+               SV("1986-09-28 03:00:00 CET"));
+  }
+
+  { // offset pointer
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{}, std::chrono::sys_seconds{})),
+               SV("1970-01-01 00:00:00 +00s"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{"42"}, std::chrono::sys_seconds{})),
+               SV("1969-12-31 23:59:18 +42s"));
+
+    TEST_EQUAL(stream_fr_FR_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{"-42"}, std::chrono::sys_seconds{})),
+               SV("1970-01-01 00:00:42 -42s"));
+  }
+}
+
+template <class CharT>
+static void test_ja_JP() {
+  using namespace std::literals::chrono_literals;
+
+  { //  Different durations
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::nanoseconds>{42ns})),
+               SV("1970-01-01 01:00:00.000000042 +01"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::microseconds>{42us})),
+               SV("1970-01-01 01:00:00.000042 +01"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::milliseconds>{42ms})),
+               SV("1970-01-01 01:00:00.042 +01"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(
+                   std::chrono::zoned_time("Etc/GMT-1", std::chrono::sys_time<std::chrono::seconds>{42s})),
+               SV("1970-01-01 01:00:42 +01"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Etc/GMT-1", std::chrono::sys_time<std::chrono::days>{std::chrono::days{42}})),
+               SV("1970-02-12 01:00:00 +01"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Etc/GMT-1", std::chrono::sys_time<std::chrono::weeks>{std::chrono::weeks{42}})),
+               SV("1970-10-22 01:00:00 +01"));
+  }
+
+  { // Daylight saving time switches
+    // Pick an historic date where it's well known what the time zone rules were.
+    // This makes it unlikely updates to the database change these rules.
+
+    // Z Europe/Berlin 0:53:28 - LMT 1893 Ap
+    // ...
+    // 1 DE CE%sT 1980
+    // 1 E CE%sT
+    //
+    // ...
+    // R E 1979 1995 - S lastSu 1u 0 -
+    // R E 1981 ma - Mar lastSu 1u 1 S
+
+    // Pick an historic date where it's well known what the time zone rules were.
+    // This makes it unlikely updates to the database change these rules.
+
+    // Start of daylight saving time
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::March / 30 / 1986} + 0h + 59min + 59s)),
+               SV("1986-03-30 01:59:59 CET"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::March / 30 / 1986} + 1h)),
+               SV("1986-03-30 03:00:00 CEST"));
+
+    // End of daylight saving time
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 0h + 59min + 59s)),
+               SV("1986-09-28 02:59:59 CEST"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 1h)),
+               SV("1986-09-28 02:00:00 CET"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 1h + 59min + 59s)),
+               SV("1986-09-28 02:59:59 CET"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   "Europe/Berlin", std::chrono::sys_days{std::chrono::September / 28 / 1986} + 2h)),
+               SV("1986-09-28 03:00:00 CET"));
+  }
+
+  { // offset pointer
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{}, std::chrono::sys_seconds{})),
+               SV("1970-01-01 00:00:00 +00s"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{"42"}, std::chrono::sys_seconds{})),
+               SV("1969-12-31 23:59:18 +42s"));
+
+    TEST_EQUAL(stream_ja_JP_locale<CharT>(std::chrono::zoned_time(
+                   offset_time_zone<offset_time_zone_flags::none>{"-42"}, std::chrono::sys_seconds{})),
+               SV("1970-01-01 00:00:42 -42s"));
+  }
+}
+
+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;
+}

>From d92b3e184d9cb9eb1167d77c8bbe4f16666ca8a5 Mon Sep 17 00:00:00 2001
From: Mark de Wever <koraq at xs4all.nl>
Date: Wed, 17 Jul 2024 18:43:30 +0200
Subject: [PATCH 2/2] Addresses review comments.

---
 libcxx/include/__chrono/formatter.h                          | 2 +-
 libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp  | 2 +-
 .../time.zone.zonedtime.nonmembers/ostream.pass.cpp          | 5 ++++-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/libcxx/include/__chrono/formatter.h b/libcxx/include/__chrono/formatter.h
index 161e5433723a2..3f678a543ac68 100644
--- a/libcxx/include/__chrono/formatter.h
+++ b/libcxx/include/__chrono/formatter.h
@@ -963,7 +963,7 @@ struct formatter<chrono::local_info, _CharT> : public __formatter_chrono<_CharT>
 // Note due to how libc++'s formatters are implemented there is no need to add
 // the exposition only local-time-format-t abstraction.
 template <class _Duration, class _TimeZonePtr, __fmt_char_type _CharT>
-struct formatter< chrono::zoned_time<_Duration, _TimeZonePtr>, _CharT> : public __formatter_chrono<_CharT> {
+struct formatter<chrono::zoned_time<_Duration, _TimeZonePtr>, _CharT> : public __formatter_chrono<_CharT> {
 public:
   using _Base = __formatter_chrono<_CharT>;
 
diff --git a/libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp b/libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp
index 98d14cbfa9005..1e366ac72fa9f 100644
--- a/libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp
+++ b/libcxx/test/std/time/time.syn/formatter.zoned_time.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: no-localization
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
 
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
diff --git a/libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp
index 82fd2e7b9f26c..06131d66c0f5c 100644
--- a/libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.zone/time.zone.zonedtime/time.zone.zonedtime.nonmembers/ostream.pass.cpp
@@ -7,13 +7,16 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: no-localization
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
 
 // TODO FMT This test should not require std::to_chars(floating-point)
 // XFAIL: availability-fp_to_chars-missing
 
 // XFAIL: libcpp-has-no-experimental-tzdb
 
+// REQUIRES: locale.fr_FR.UTF-8
+// REQUIRES: locale.ja_JP.UTF-8
+
 // <chrono>
 
 // template<class charT, class traits, class Duration, class TimeZonePtr>



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