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< c‎ | chrono

Compiler support

Program utilities

Variadic function support

Dynamic memory management

Strings library

Date and time utilities

Input/output support

Localization support

Concurrency support (C11)

Technical Specifications

Date and time utilities

Functions

Time manipulation

(C11)

timespec_getres

(C23)

Format conversions

asctimeasctime_s

(deprecated in C23)(C11)

(deprecated in C23)(C11)

(C95)

gmtimegmtime_rgmtime_s

(C23)(C11)

localtimelocaltime_rlocaltime_s

(C23)(C11)

Constants

Types

tm

(C11)

Defined in header <time.h>

struct tm;

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

Contents

[edit] Member objects

int tm_sec

seconds after the minute – [0, 61](until C99)[0, 60](since C99)^{[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)

[edit] Notes

The Standard mandates only the presence of the aforementioned members in either 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 C89 range 0..61 was a defect)

[edit] Example

Run this code

#include <stdio.h>
#include <time.h>
 
int main(void)
{
 struct tm start = {.tm_year = 2022 - 1900, .tm_mday = 1};
 mktime (&start);
 printf ("%s", asctime (&start)); // note implicit trailing '\n'
}

Output:

Sat Jan 1 00:00:00 2022

[edit] References

C23 standard (ISO/IEC 9899:2024):

7.27.1/3 Components of time (p: TBD)

C17 standard (ISO/IEC 9899:2018):

7.27.1/3 Components of time (p: 284)

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

[edit] See also

localtimelocaltime_rlocaltime_s

(C23)(C11)

converts time since epoch to calendar time expressed as local time
(function) [edit]

gmtimegmtime_rgmtime_s

(C23)(C11)

converts time since epoch to calendar time expressed as Coordinated Universal Time (UTC)
(function) [edit]

C++ documentation for tm

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