C standard library time.h

The time.h header defines four variable types, two macro and various functions for manipulating date and time.

Library Variables

size_t

This is the unsigned integral type and is the result of the sizeof keyword.

clock_t

This is a type suitable for storing the processor time.

time_t is

This is a type suitable for storing the calendar time.

struct tm

This is a structure used to hold the time and date.

Library Macros

NULL

This macro is the value of a null pointer constant.

CLOCKS_PER_SEC

This macro represents the number of processor clocks per second.

Library Functions

char *asctime(const struct tm *timeptr)

Returns a pointer to a string which represents the day and time of the structure timeptr.

clock_t clock(void)

Returns the processor clock time used since the beginning of an implementation defined era (normally the beginning of the program).

char *ctime(const time_t *timer)

Returns a string representing the localtime based on the argument timer.

double difftime(time_t time1, time_t time2)

Returns the difference of seconds between time1 and time2 (time1-time2).

struct tm *gmtime(const time_t *timer)

The value of timer is broken up into the structure tm and expressed in Coordinated Universal Time (UTC) also known as Greenwich Mean Time (GMT).

struct tm *localtime(const time_t *timer)

The value of timer is broken up into the structure tm and expressed in the local time zone.

time_t mktime(struct tm *timeptr)

Converts the structure pointed to by timeptr into a time_t value according to the local time zone.

size_t strftime(char *str, size_t maxsize, const char *format, const struct tm *timeptr)

Formats the time represented in the structure timeptr according to the formatting rules defined in format and stored into str.

time_t time(time_t *timer)

Calculates the current calender time and encodes it into time_t format.