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# Time Functions (time.h)

The following documentation discusses functions used either for reporting on time (elapsed, current, or compute time) or to perform calculations based on time.

asctime

clock

ctime

difftime

gmtime

localtime

mktime

strftime

time

The header file, time.h, defines three types. clock_t and time_t are both used for representations of time particularly suitable for arithmetic. (In this implementation, quantities of type, clock_t, have the highest resolution possible on your machine, and quantities of type, time_t, resolve to seconds.) size_t is also defined if necessary for quantities representing sizes.

time.h also defines the structure, tm, for the traditional representation of Gregorian calendar time as a series of numbers, with the following fields.

tm_sec | Seconds.
tm_min | Minutes.
tm_hour | Hours.
tm_mday | Day.
tm_mon | Month.
tm_year | Year (since 1900).
tm_wday | Day of week: the number of days since Sunday.
tm_yday | Number of days elapsed since last January 1.
tm_isdst | Daylight Savings Time flag: positive means DST in effect, zero means DST not in effect, negative means no information about DST is available.