std::chrono::time_point_cast

 

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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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std::chrono::time_point

Member functions

time_point::time_point

time_point::time_since_epoch

time_point::operator+=time_point::operator-=

time_point::operator++time_point::operator-- (C++20)(C++20)

time_point::min

time_point::max

Non-member functions

operator+operator-

operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(C++20)

time_point_cast

floor (C++17)

ceil (C++17)

round (C++17)

Helper classes

common_type

hash<std::chrono::time_point> (C++26)

 

Defined in header <chrono>
template< class ToDuration, class Clock, class Duration > std::chrono::time_point<Clock, ToDuration> time_point_cast( const std::chrono::time_point<Clock, Duration> &t );		(since C++11) (until C++14)
template< class ToDuration, class Clock, class Duration > constexpr std::chrono::time_point<Clock, ToDuration> time_point_cast( const std::chrono::time_point<Clock, Duration> &t );			(since C++14)

Converts a std::chrono::time_point from one duration to another.

time_point_cast participates in overload resolution only if ToDuration is a specialization of std::chrono::duration.

Parameters

t

-

time_point to convert from

Return value

std::chrono::time_point<Clock, ToDuration>( std::chrono::duration_cast<ToDuration>(t.time_since_epoch())).

Example

Run this code

#include <chrono>
#include <iostream>
using namespace std::chrono_literals;

using Clock = std::chrono::high_resolution_clock;
using Ms = std::chrono::milliseconds;
using Sec = std::chrono::seconds;

template<class Duration>
using TimePoint = std::chrono::time_point<Clock, Duration>;

inline void print_ms(const TimePoint<Ms>& time_point)
{
    std::cout << time_point.time_since_epoch().count() << " ms\n";
}

int main()
{
    TimePoint<Sec> time_point_sec{4s};

    // implicit conversion, no precision loss
    TimePoint<Ms> time_point_ms = time_point_sec;
    print_ms(time_point_ms); // 4000 ms

    time_point_ms = TimePoint<Ms>{5756ms};
    print_ms(time_point_ms); // 5756 ms

    // explicit cast, need when precision loss may happen
    // 5756 truncated to 5000
    time_point_sec = std::chrono::time_point_cast<Sec>(time_point_ms);
    print_ms(time_point_sec); // 5000 ms
}

Output:

4000 ms
5756 ms
5000 ms

See also

floor(std::chrono::time_point) (C++17)	converts a time_point to another, rounding down (function template)
ceil(std::chrono::time_point) (C++17)	converts a time_point to another, rounding up (function template)
round(std::chrono::time_point) (C++17)	converts a time_point to another, rounding to nearest, ties to even (function template)
duration_cast (C++11)	converts a duration to another, with a different tick interval (function template)