### <time.h>

The <time.h> include file declares the time and date functions:

asctime | ctime | gmtime | mktime | strptime
clock | difftime | localtime | strftime | time

In extended mode, <time.h> also defines the standard extensions _strdate, _strtime, and tzset.

<time.h> also provides:

- A structure tm containing the components of a calendar time. See gmtime -- Convert Time for a list of the members of the tm structure.
- A macro CLOCKS_PER_SEC equal to the number per second of the value returned by the clock function.
- Types clock_t, time_t, and size_t.
- The NULL pointer value.

For more information on NULL and the type size_t, see <stddef.h>.

<time.h> also defines the global variables _daylight, _timezone, and _tzname.

gmtime -- Convert Time
<stddef.h>
#include