tm

 

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Atomic operations (C11)

Thread support (C11)

Technical Specifications

 

Date and time utilities

Functions

Time manipulation

difftime

time

clock

timespec_get (C11)

Format conversions

asctimeasctime_s (C11)

ctimectime_s (C11)

strftime

wcsftime (C95)

gmtimegmtime_s (C11)

localtimelocaltime_s (C11)

mktime

Constants

CLOCKS_PER_SEC

Types

tm

time_t

clock_t

timespec (C11)

 

Defined in header <time.h>
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 C99) / [0, 60] (since C99)
int tm_min	minutes after the hour – [0, 59]
int tm_hour	hours since midnight – [0, 23]
int tm_mday	day of the month – [1, 31]
int tm_mon	months since January – [0, 11]
int tm_year	years since 1900
int tm_wday	days since Sunday – [0, 6]
int tm_yday	days since January 1 – [0, 365]
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

Example

Show the start of calendar time.

Run this code

#include <stdio.h>
#include <time.h>
 
int main(void)
{
    struct tm start = {.tm_mday=1};
    mktime(&start);
    printf("%s\n", asctime(&start));
}

Possible output:

Mon Jan  1 00:00:00 1900

References

• C11 standard (ISO/IEC 9899:2011):

• 7.27.1/3 Components of time (p: 388)

• C99 standard (ISO/IEC 9899:1999):

• 7.23.1/3 Components of time (p: 338)

• C89/C90 standard (ISO/IEC 9899:1990):

• 4.12.1 Components of time

See also

localtimelocaltime_s (C11)	converts time since epoch to calendar time expressed as local time (function)
gmtimegmtime_s (C11)	converts time since epoch to calendar time expressed as Coordinated Universal Time (UTC) (function)