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std::chrono::zoned_time

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< cpp‎ | chrono
 
 
Date and time library
Time point
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Time of day
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Calendar
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chrono I/O
(C++20)

Time zone
(C++20)
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(C++20)
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(C++20)
zoned_time
(C++20)
(C++20)
C-style date and time
 
 
Defined in header <chrono>
template<

    class Duration,
    class TimeZonePtr = const std::chrono::time_zone *

> class zoned_time;
(since C++20)
using zoned_seconds = std::chrono::zoned_time<std::chrono::seconds >;
(since C++20)

The class zoned_time represents a logical pairing of a time zone and a std::chrono::time_point whose resolution is Duration.

An invariant of zoned_time is that it always refers to a valid time zone and represents an existing and unambiguous time point in that time zone. Consistent with this invariant, zoned_time has no move constructor or move assignment operator; attempts to move a zoned_time will perform a copy.

The program is ill-formed if Duration is not a specialization of std::chrono::duration .

The template parameter TimeZonePtr allows users to supply their own time zone pointer types and further customize the behavior of zoned_time via std::chrono::zoned_traits. Custom time zone types need not support all the operations supported by std::chrono::time_zone, only those used by the functions actually called on the zoned_time.

TimeZonePtr must be MoveConstructible. Move-only TimeZonePtrs are allowed but difficult to use, as the zoned_time will be immovable and it is not possible to access the stored TimeZonePtr.

Contents

[edit] Member types

Member type Definition
duration std::common_type_t <Duration, std::chrono::seconds >

[edit] Member functions

constructs a zoned_time
(public member function) [edit]
assigns value to a zoned_time
(public member function) [edit]
obtains a copy of the time zone pointer
(public member function) [edit]
obtains the stored time point as a local_time
(public member function) [edit]
obtains the stored time point as a sys_time
(public member function) [edit]
obtain information about the time zone at the stored time point
(public member function) [edit]

[edit] Non-member functions

(C++20)
compares two zoned_time values
(function template) [edit]
(C++20)
outputs a zoned_time into a stream
(function template) [edit]

[edit] Helper classes

formatting support for zoned_time
(class template specialization) [edit]
hash support for std::chrono::zoned_time
(class template specialization)

[edit] Helper specializations

template< class Duration >

constexpr bool enable_nonlocking_formatter_optimization

  <chrono::zoned_time<Duration, const chrono::time_zone*>> = true;
(since C++23)

This specialization of std::enable_nonlocking_formatter_optimization enables efficient implementation of std::print and std::println for printing a chrono::zoned_time object.

[edit] Deduction guides

[edit] Example

Run this code
#include <algorithm>
#include <chrono>
#include <iomanip>
#include <iostream>
#include <stdexcept>
#include <string_view>
 
int main()
{
 constexpr std::string_view locations[] =
 {
 "Africa/Casablanca", "America/Argentina/Buenos_Aires",
 "America/Barbados", "America/Indiana/Petersburg",
 "America/Tarasco_Bar", "Antarctica/Casey",
 "Antarctica/Vostok", "Asia/Magadan",
 "Asia/Manila", "Asia/Shanghai",
 "Asia/Tokyo", "Atlantic/Bermuda",
 "Australia/Darwin", "Europe/Isle_of_Man",
 "Europe/Laputa", "Indian/Christmas",
 "Indian/Cocos", "Pacific/Galapagos",
 };
 
 constexpr auto width = std::ranges::max_element (locations, {},
 [](const auto& s){ return s.length(); })->length();
 
 for (const auto location : locations)
 try
 {
 // may throw if 'location' is not in the time zone database
 const std::chrono::zoned_time zt{location, std::chrono::system_clock::now ()};
 std::cout << std::setw (width) << location << " - Zoned Time: " << zt << '\n';
 }
 catch (std::runtime_error & ex)
 {
 std::cout << "Error: " << ex.what() << '\n';
 }
}

Possible output: 

 Africa/Casablanca - Zoned Time: 2023年06月29日 20:58:34.697449319 +01
America/Argentina/Buenos_Aires - Zoned Time: 2023年06月29日 16:58:34.709957354 -03
 America/Barbados - Zoned Time: 2023年06月29日 15:58:34.709977888 AST
 America/Indiana/Petersburg - Zoned Time: 2023年06月29日 15:58:34.709998072 EDT
Error: tzdb: cannot locate zone: America/Tarasco_Bar
 Antarctica/Casey - Zoned Time: 2023年06月30日 06:58:34.710093685 +11
 Antarctica/Vostok - Zoned Time: 2023年06月30日 01:58:34.710107932 +06
 Asia/Magadan - Zoned Time: 2023年06月30日 06:58:34.710121831 +11
 Asia/Manila - Zoned Time: 2023年06月30日 03:58:34.710134751 PST
 Asia/Shanghai - Zoned Time: 2023年06月30日 03:58:34.710153259 CST
 Asia/Tokyo - Zoned Time: 2023年06月30日 04:58:34.710172815 JST
 Atlantic/Bermuda - Zoned Time: 2023年06月29日 16:58:34.710191043 ADT
 Australia/Darwin - Zoned Time: 2023年06月30日 05:28:34.710236720 ACST
 Europe/Isle_of_Man - Zoned Time: 2023年06月29日 20:58:34.710256834 BST
Error: tzdb: cannot locate zone: Europe/Laputa
 Indian/Christmas - Zoned Time: 2023年06月30日 02:58:34.710360409 +07
 Indian/Cocos - Zoned Time: 2023年06月30日 02:28:34.710377520 +0630
 Pacific/Galapagos - Zoned Time: 2023年06月29日 13:58:34.710389952 -06

[edit] See also

(C++20)
represents a time zone
(class) [edit]
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