std::chrono::time_point_cast

Since C++14

Header: <chrono>

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

# Declarations

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)

# Parameters

# Return value

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

# Example

#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
}

# See also