NAME

std::chrono::time_point::time_since_epoch - std::chrono::time_point::time_since_epoch

Synopsis

duration time_since_epoch() const; (since C++11)
(until C++14)
constexpr duration time_since_epoch() const; (since C++14)

Returns a duration representing the amount of time between *this and the clock's
epoch.

Parameters

(none)

Return value

The amount of time between this time_point and the clock's epoch

Example

// Run this code

#include <iostream>
#include <chrono>
#include <ctime>

int main()
{
const auto p0 = std::chrono::time_point<std::chrono::system_clock>{};
const auto p1 = std::chrono::system_clock::now();
const auto p2 = p1 - std::chrono::hours(24);

std::time_t epoch_time = std::chrono::system_clock::to_time_t(p0);
std::cout << "epoch: " << std::ctime(&epoch_time);
std::time_t today_time = std::chrono::system_clock::to_time_t(p1);
std::cout << "today: " << std::ctime(&today_time);

std::cout << "hours since epoch: "
<< std::chrono::duration_cast<std::chrono::hours>(
p1.time_since_epoch()).count()
<< '\n';
std::cout << "yesterday, hours since epoch: "
<< std::chrono::duration_cast<std::chrono::hours>(
p2.time_since_epoch()).count()
<< '\n';
}

Possible output:

epoch: Thu Jan 1 00:00:00 1970
today: Fri Jun 30 10:44:11 2017
hours since epoch: 416338
yesterday, hours since epoch: 416314