# time_t

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< c‎ | chrono

Defined in header `<time.h>` |  |
typedef /* unspecified */ time_t; |  |

Real arithmetic type capable of representing times.

Although not defined by the C standard, this is almost always an integral value holding the number of seconds (not counting leap seconds) since 00:00, Jan 1 1970 UTC, corresponding to POSIX time.

### Notes

The standard uses the term calendar time when referring to a value of type time_t.

### Example

Show the start of the epoch.

Run this code

    #include <stdio.h>
    #include <time.h>
    #include <stdint.h>

    int main(void)
    {
        time_t epoch = 0;
        printf("%jd seconds since the epoch began\n", (intmax_t)epoch);
        printf("%s", asctime(gmtime(&epoch)));
    }

Possible output:

    0 seconds since the epoch began
    Thu Jan  1 00:00:00 1970

### References

- 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

### See also

time | returns the current calendar time of the system as time since epoch (function)
localtime localtime_r localtime_s (C23)(C11) | converts time since epoch to calendar time expressed as local time (function)
gmtime gmtime_r gmtime_s (C23)(C11) | converts time since epoch to calendar time expressed as Coordinated Universal Time (UTC) (function)

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