Table of Contents

C Library – <time.h>

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

Library Variables

Following are the variable types defined in the header time.h −

Sr.No.	Variable & Description
1	size_t This is the unsigned integral type and is the result of the sizeof keyword.
2	clock_t This is a type suitable for storing the processor time.
3	time_t is This is a type suitable for storing the calendar time.
4	struct tm This is a structure used to hold the time and date.

Following are the macros defined in the header time.h −

Sr.No.	Macro & Description
1	NULL This macro is the value of a null pointer constant.
2	CLOCKS_PER_SEC This macro represents the number of processor clocks per second.

Sr.No.

Macro & Description

NULL

This macro is the value of a null pointer constant.

CLOCKS_PER_SEC

This macro represents the number of processor clocks per second.

Following are the functions defined in the header time.h −

Sr.No.	Function & Description
1	char asctime(const struct tm timeptr) Returns a pointer to a string which represents the day and time of the structure timeptr.
2	clock_t clock(void) Returns the processor clock time used since the beginning of an implementation defined era (normally the beginning of the program).
3	char ctime(const time_t timer) Returns a string representing the localtime based on the argument timer.
4	double difftime(time_t time1, time_t time2) Returns the difference of seconds between time1 and time2 (time1-time2).
5	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).
6	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.
7	time_t mktime(struct tm *timeptr) Converts the structure pointed to by timeptr into a time_t value according to the local time zone.
8	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.
9	time_t time(time_t *timer) Calculates the current calender time and encodes it into time_t format.
10	size_t wcsftime( wchar_t* str, size_t count, const wchar_t* format, const struct tm* time ) Converts a tm object to custom wide string textual representation.

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