std::mktime

Converts local calendar time to a time since epoch as a std::time_t object. time->tm_wday and time->tm_yday are ignored. The values in time

A negative value of time->tm_isdst causes mktime

If the conversion is successful, the time object is modified. All fields of time are updated to fit their proper ranges. time->tm_wday and time->tm_yday

Parameters

Return value

Time since epoch as a std::time_t object on success or -1 if time cannot be represented as a std::time_t

Notes

If the std::tm object was obtained from std::get_time or the POSIX strptime, the value of tm_isdst is indeterminate, and needs to be set explicitly before calling mktime

Example

#include <ctime>
#include <iomanip>
#include <iostream>
#include <sstream>
 
int main()
{
    setenv("TZ", "/usr/share/zoneinfo/America/Los_Angeles", 1); // POSIX-specific
 
    std::tm tm{}; // Zero initialise
    tm.tm_year = 2020 - 1900; // 2020
    tm.tm_mon = 2 - 1; // February
    tm.tm_mday = 15; // 15th
    tm.tm_hour = 10;
    tm.tm_min = 15;
    tm.tm_isdst = 0; // Not daylight saving
    std::time_t t = std::mktime(&tm); 
    std::tm local = *std::localtime(&t);
 
    std::cout << "local: " << std::put_time(&local, "%c %Z") << '\n';
}

local: Sat Feb 15 10:15:00 2020 PST

See also