std::chrono::system_clock::to_time_t

 

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Date and time library

Time point time_point (C++11) clock_time_conversion (C++20)   clock_cast (C++20) Duration duration (C++11) Clocks system_clock (C++11) steady_clock (C++11) is_clock (C++20) utc_clock (C++20) tai_clock (C++20) high_resolution_clock (C++11) gps_clock (C++20) file_clock (C++20) local_t (C++20) Time of day is_amis_pm (C++20)(C++20) make12make24 (C++20)(C++20) hh_mm_ss (C++20)

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Time zone tzdb (C++20) tzdb_list (C++20) get_tzdbget_tzdb_listreload_tzdbremote_version (C++20)(C++20)(C++20)(C++20) sys_info (C++20) local_info (C++20) nonexistent_local_time (C++20) ambiguous_local_time (C++20) locate_zone (C++20) current_zone (C++20) time_zone (C++20) choose (C++20) zoned_traits (C++20) zoned_time (C++20) time_zone_link (C++20) leap_second (C++20) leap_second_info (C++20) get_leap_second_info (C++20) C-style date and time

 

std::chrono::system_clock

Member functions

system_clock::now

system_clock::to_time_t

system_clock::from_time_t

Time point I/O

operator<<

formatter<std::chrono::sys_time>

from_stream

 

static std::time_t to_time_t( const time_point& t ) noexcept;		(since C++11)

Converts t to a std::time_t type.

If std::time_t has lower precision, it is implementation-defined whether the value is rounded or truncated.

Parameters

t

-

system clock time point to convert

Return value

A std::time_t value representing t.

Example

Get the current time as a std::time_t two ways.

Run this code

#include <chrono>
#include <ctime>
#include <iostream>
#include <thread>
using namespace std::chrono_literals;
 
int main()
{
    / The old way
    std::time_t oldt = std::time({});
 
    std::this_thread::sleep_for(2700ms);
 
    / The new way
    auto const now = std::chrono::system_clock::now();
    std::time_t newt = std::chrono::system_clock::to_time_t(now);
 
    std::cout << "newt - oldt == " << newt - oldt << " s\n";
}

Possible output:

newt - oldt == 3 s

See also

from_time_t [static]

converts std::time_t to a system clock time point (public static member function)

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