Defined in header <ctime>
double difftime( std::time_t time_end, std::time_t time_beg );

Computes difference between two calendar times as std::time_t objects (time_end - time_beg) in seconds. If time_end refers to time point before time_beg then the result is negative.


time_beg, time_end - times to compare

Return value

Difference between two times in seconds.


On POSIX systems, std::time_t is measured in seconds, and difftime is equivalent to arithmetic subtraction, but C and C++ allow fractional units for time_t.


#include <iostream>
#include <ctime>
int main()
    std::time_t start = std::time(nullptr);
    volatile double d = 1.0;
    // some time-consuming operation
    for (int p=0; p<10000; ++p) {
        for (int q=0; q<100000; ++q) {
           d = d+p*d*q+d;
    std::cout << "Wall time passed: "
              << std::difftime(std::time(nullptr), start) << " s.\n";

Possible output:

Wall time passed: 9 s.

See also

a time interval
(class template)
C documentation for difftime

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.