Namespaces
Variants

    std::difftime

    From cppreference.com
    < cpp | chrono | c
     
    C++
     
    Date and time library
    Time point
    (C++11)
    (C++20)  
    (C++20)
    Duration
    (C++11)
    Clocks
    (C++11)
    (C++11)
    (C++20)
    (C++20)
    (C++20)
    (C++11)
    (C++20)
    (C++20)
    (C++20)
    Time of day
    (C++20)(C++20)
    (C++20)(C++20)
    (C++20)
    Calendar
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)  
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)
    (C++20)(C++20)
    chrono I/O
    (C++20)

     
    C-style date and time utilities
    Functions
    Time manipulation
    (C++17)
    (C++26)
    Format conversions
    (deprecated in C++26)
    (deprecated in C++26)
    Constants
    Types
    (C++17)
     
    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.

    Parameters

    time_beg, time_end - times to compare

    Return value

    Difference between two times in seconds.

    Notes

    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.

    Example

    Run this code
    #include <ctime>
#include <iostream>

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

    (C++11)
    		 a time interval
    (class template) [edit]
    C documentation for difftime