| Data Type | Declared In | Contains | Some Functions Using this Type |
|---|
| time_t | time.h | long int with time in seconds since 00:00:00 UTC, January 1, 1970 | time(2), ctime(3C), cftime(3C), difftime(3C) |
| timeval | sys/time.h | time_t of seconds, long of microseonds | adjtime(2), getitimer(2), getrusage(3C), gettimeofday(3C), select(2), utimes(3B), utmpx(4) |
| itimerval | sys/time.h | two timeval fields for first interval and repeat interval | getitimer(2) and setitimer(2) |
| timespec_t | time.h | time_t of seconds, long of nanoseconds | clock_gettime(2), nanosleep(2), aio_suspend(3), sigtimedwait(3) |
| itimerspec | time.h | two timespec fields for first interval and repeat interval | (none at this time) |
| tm | time.h | int fields for seconds, minutes, hours, day, month, year, etc. | localtime(2), gmtime(2), strftime(3C) |