std::tm

Defined in header `<ctime>`
struct tm;

Structure holding a calendar date and time broken down into its components.

Member objects

int tm_sec	seconds after the minute – `[0,` `61]`(until C++11) `[0,` `60]`(since C++11)^{[note 1]} (public member object)
int tm_min	minutes after the hour – `[0,` `59]` (public member object)
int tm_hour	hours since midnight – `[0,` `23]` (public member object)
int tm_mday	day of the month – `[1,` `31]` (public member object)
int tm_mon	months since January – `[0,` `11]` (public member object)
int tm_year	years since 1900 (public member object)
int tm_wday	days since Sunday – `[0,` `6]` (public member object)
int tm_yday	days since January 1 – `[0,` `365]` (public member object)
int tm_isdst	Daylight Saving Time flag. The value is positive if DST is in effect, zero if not and negative if no information is available. (public member object)

Notes

The Standard mandates only the presence of the aforementioned members in some order. The implementations usually add more data members to this structure.

Range allows for a positive leap second. Two leap seconds in the same minute are not allowed (the range [0, 61] was a defect introduced in C89 and corrected in C99).

Example

#include <ctime>
#include <iostream>
 
int main()
{
    std::tm tm{};
    tm.tm_year = 2022 - 1900;
    tm.tm_mday = 1;
    std::mktime(&tm);
 
    std::cout << std::asctime(&tm); // note implicit trailing '\n'
 
    std::cout << "sizeof(std::tm) = " << sizeof(std::tm) << '\n'
              << "sum of sizes of standard members = "
              << sizeof(tm.tm_sec) +
                 sizeof(tm.tm_min) +
                 sizeof(tm.tm_hour) +
                 sizeof(tm.tm_mday) +
                 sizeof(tm.tm_mon) +
                 sizeof(tm.tm_year) +
                 sizeof(tm.tm_wday) +
                 sizeof(tm.tm_yday) +
                 sizeof(tm.tm_isdst) << '\n';
}

Possible output:

Sat Jan  1 00:00:00 2022
sizeof(std::tm) = 56
sum of sizes of standard members = 36

localtime	converts time since epoch to calendar time expressed as local time (function)
gmtime	converts time since epoch to calendar time expressed as Universal Coordinated Time (function)
C documentation for `tm`

std::tm

Member objects

Notes

Example

See also