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std::chrono::time_point

Defined in header `<chrono>`
template< class Clock, class Duration = typename Clock::duration > class time_point;		(since C++11)

Class template std::chrono::time_point represents a point in time. It is implemented as if it stores a value of type Duration indicating the time interval from the start of the Clock's epoch.

Clock must meet the requirements for Clock or be std::chrono::local_t (since C++20).

(until C++23)

Member types

Member type	Definition
`clock`	`Clock`, the clock on which this time point is measured
`duration`	`Duration`, a `std::chrono::duration` type used to measure the time since epoch
`rep`	`Rep`, an arithmetic type representing the number of ticks of the duration
`period`	`Period`, a `std::ratio` type representing the tick period of the duration

Member functions

(constructor)	constructs a new time point (public member function)
time_since_epoch	returns the time point as duration since the start of its clock (public member function)
operator+=operator-=	modifies the time point by the given duration (public member function)
operator++operator++(int)operator--operator--(int) (C++20)	increments or decrements the duration (public member function)
min [static]	returns the time point corresponding to the smallest duration (public static member function)
max [static]	returns the time point corresponding to the largest duration (public static member function)

Non-member functions

operator+operator- (C++11)	performs add and subtract operations involving a time point (function template)
operator==operator!=operator<operator<=operator>operator>=operator<=> (C++11)(C++11)(removed in C++20)(C++11)(C++11)(C++11)(C++11)(C++20)	compares two time points (function template)
time_point_cast (C++11)	converts a time point to another time point on the same clock, with a different duration (function template)
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)

Helper classes

std::common_type<std::chrono::time_point>

(C++11)

specializes the std::common_type trait
(class template specialization)

Example

#include <algorithm>
#include <chrono>
#include <ctime>
#include <iomanip>
#include <iostream>
 
void slow_motion()
{
    static int a[] {1,2,3,4,5,6,7,8,9,10,11,12};
    // Generate Γ(13) == 12! permutations:
    while (std::ranges::next_permutation(a).found) { }
}
 
int main()
{
    using namespace std::literals; // enables the usage of 24h, 1ms, 1s instead of
                                   // e.g. std::chrono::hours(24), accordingly
    const std::chrono::time_point<std::chrono::system_clock> now =
        std::chrono::system_clock::now();
 
    const std::time_t t_c = std::chrono::system_clock::to_time_t(now - 24h);
    std::cout << "24 hours ago, the time was "
              << std::put_time(std::localtime(&t_c), "%F %T.\n") << std::flush;
 
    const std::chrono::time_point<std::chrono::steady_clock> start =
        std::chrono::steady_clock::now();
 
    std::cout << "Different clocks are not comparable: \n"
                 "  System time: " << now.time_since_epoch() << "\n"
                 "  Steady time: " << start.time_since_epoch() << '\n';
 
    slow_motion();
 
    const auto end = std::chrono::steady_clock::now();
    std::cout
        << "Slow calculations took "
        << std::chrono::duration_cast<std::chrono::microseconds>(end - start) << " ≈ "
        << (end - start) / 1ms << "ms ≈ " // almost equivalent form of the above, but
        << (end - start) / 1s << "s.\n";  // using milliseconds and seconds accordingly
}

Possible output:

24 hours ago, the time was 2021-02-15 18:28:52.
Different clocks are not comparable:
  System time: 1666497022681282572ns
  Steady time: 413668317434475ns
Slow calculations took 2090448µs ≈ 2090ms ≈ 2s.