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std::chrono::zoned_time<Duration,TimeZonePtr>::zoned_time

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< cpp‎ | chrono‎ | zoned time
 
 
Utilities library
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zoned_time();
(1) (since C++20)
zoned_time( const std::chrono::sys_time<Duration>& st );
(2) (since C++20)
zoned_time( const zoned_time& other) = default;
(3) (since C++20)
template< class Duration2 >
zoned_time( const std::chrono::zoned_time<Duration2, TimeZonePtr>& other );
(4) (since C++20)
explicit zoned_time( TimeZonePtr z );
(5) (since C++20)
explicit zoned_time( std::string_view name );
(6) (since C++20)
zoned_time( TimeZonePtr z, const std::chrono::sys_time<Duration>& st );
(7) (since C++20)
zoned_time( std::string_view name, const std::chrono::sys_time<Duration>& st );
(8) (since C++20)
zoned_time( TimeZonePtr z, const std::chrono::local_time<Duration>& tp );
(9) (since C++20)
zoned_time( std::string_view name, const std::chrono::local_time<Duration>& tp );
(10) (since C++20)
zoned_time( TimeZonePtr z, const std::chrono::local_time<Duration>& tp,
            std::chrono::choose c );
(11) (since C++20)
zoned_time( std::string_view name,
            const std::chrono::local_time<Duration>& tp, std::chrono::choose c );
(12) (since C++20)
template< class Duration2, class TimeZonePtr2 >

zoned_time( TimeZonePtr z,

            const std::chrono::zoned_time<Duration2, TimeZonePtr2>& zt );
(13) (since C++20)
template< class Duration2, class TimeZonePtr2 >

zoned_time( TimeZonePtr z,
            const std::chrono::zoned_time<Duration2, TimeZonePtr2>& zt,

            std::chrono::choose );
(14) (since C++20)
template< class Duration2, class TimeZonePtr2 >

zoned_time( std::string_view name,

            const std::chrono::zoned_time<Duration2, TimeZonePtr2>& zt );
(15) (since C++20)
template< class Duration2, class TimeZonePtr2 >

zoned_time( std::string_view name,
            const std::chrono::zoned_time<Duration2, TimeZonePtr2>& zt,

            std::chrono::choose );
(16) (since C++20)

Constructs a zoned_time object, initializing the stored time zone pointer and time point according to the following table, where traits is std::chrono::zoned_traits<TimeZonePtr>:

Overload Time zone pointer (denoted zone) Time point (a std::chrono::sys_time<duration>) Notes
(1) traits::default_zone() default constructed (a)
(2) st
(3) other.get_time_zone() other.get_sys_time() (b)
(4) other.get_time_zone() other.get_sys_time() (e)
(5) std::move(z) default constructed
(6) traits::locate_zone(name) (c)
(7) std::move(z) st
(8) traits::locate_zone(name) (c)
(9) std::move(z) zone->to_sys(tp) (d)
(10) traits::locate_zone(name) (c,d)
(11) std::move(z) zone->to_sys(tp, c) (d)
(12) traits::locate_zone(name) (c,d)
(13-14) std::move(z) zt.get_sys_time() (e)
(15-16) traits::locate_zone(name) (c,e)
a) Constructors specified to call traits::default_zone() (1-2) do not participate in overload resolution if that expression is not well-formed.
b) The defaulted copy constructor (3) is defined as deleted if std::is_copy_constructible_v<TimeZonePtr> is false.
c) Constructors with a std::string_view parameter name (6,8,10,12,15-16) do not participate in overload resolution if traits::locate_zone(name) is not well-formed or if that expression is not convertible to TimeZonePtr.
d) Constructors specified to call zone->to_sys (9-12) do not participate in overload resolution if that call expression is not well-formed or if the result is not convertible to std::chrono::sys_time<duration>.
e) Constructors with a template parameter Duration2 (4,13-16) do not participate in overload resolution if Duration2 is not convertible to Duration.

The behavior is undefined if the time zone pointer (initialized as described above) does not refer to a time zone.

[edit] Notes

zoned_time does not have a move constructor and attempting to move one will perform a copy instead using the defaulted copy constructor (3). Thus, when TimeZonePtr is a move-only type, zoned_time is immovable: it can be neither moved nor copied.

The constructors (14,16) accept a std::chrono::choose parameter, but that parameter has no effect.

[edit] Example

#include <chrono>
#include <iostream>
#include <string_view>
 
int main()
{
    using std::chrono_literals::operator""y;
    using std::operator""sv;
 
    const auto now = std::chrono::floor<std::chrono::minutes>(std::chrono::system_clock::now());
 
    {
        std::cout << std::chrono::zoned_time{} << " : default\n";
    }
    {
        constexpr std::string_view location {"America/Phoenix"sv};
        std::cout << std::chrono::zoned_time{ location } << " : " << location << '\n';
    }
    {
        const std::chrono::time_zone* TimeZonePtr = std::chrono::locate_zone("UTC");
        std::cout << std::chrono::zoned_time{ TimeZonePtr } << " : UTC time zone\n";
    }
    {
        constexpr auto location{"Europe/Rome"sv};
        std::cout << std::chrono::zoned_time{ location, std::chrono::local_days{2021y/12/31} }
                  << " : " << location << '\n';
    }
    {
        constexpr auto location {"Europe/Rome"sv};
        constexpr auto some_date = std::chrono::sys_time<std::chrono::days>{2021y/12/31};
        std::cout << std::chrono::zoned_time{ location, some_date } << " : " << location << '\n';
    }
    {
        constexpr auto location {"Europe/Rome"sv};
        std::cout << std::chrono::zoned_time{ location, now } << " : " << location << '\n';
    }
    {
        constexpr auto NewYork {"America/New_York"sv};
        constexpr auto Tokyo {"Asia/Tokyo"sv};
        const std::chrono::zoned_time tz_Tokyo {Tokyo, now};
        const std::chrono::zoned_time tz_NewYork {NewYork, now};
        std::cout << std::chrono::zoned_time{ Tokyo, tz_NewYork } << " : " << Tokyo << '\n';
        std::cout << std::chrono::zoned_time{ NewYork, tz_Tokyo } << " : " << NewYork << '\n';
    }
}

Possible output:

1970-01-01 00:00:00 UTC : default
1969-12-31 17:00:00 MST : America/Phoenix
1970-01-01 00:00:00 UTC : UTC time zone
2021-12-31 00:00:00 CET : Europe/Rome
2021-12-31 01:00:00 CET : Europe/Rome
2021-09-20 23:04:00 CEST : Europe/Rome
2021-09-21 06:04:00 JST : Asia/Tokyo
2021-09-20 17:04:00 EDT : America/New_York