C date and time functions

The C date and time functions are a group of functions in the standard library of the C programming language implementing date and time manipulation operations. They provide support for time acquisition, conversion between date formats, and formatted output to strings.

Overview of functions

The C date and time operations are defined in the time.h header file (ctime header in C++).

	Identifier	Description
Time manipulation	difftime	computes the difference in seconds between two time_t objects
	time	returns the current time of the system as a time_t object (which is usually time since an epoch, typically the Unix epoch)
	clock	returns a processor tick count associated with the process
Format conversions	asctime	converts a tm object to a textual representation (deprecated)
	ctime	converts a time_t object to a textual representation
	strftime	converts a tm object to custom textual representation
	wcsftime	converts a tm object to custom wide string textual representation
	gmtime	converts a time_t object to calendar time expressed as Coordinated Universal Time
	localtime	converts a time_t object to calendar time expressed as local time
	mktime	converts calendar time to a time_t object
Constants	CLOCKS_PER_SEC	number of processor clock ticks per second
Types	struct tm	broken-down calendar time type: year, month, day, hour, minute, second
	time_t	arithmetic time type (typically time since the epoch)
	clock_t	process running time type

Example

The following C source code snippet prints the current time to the standard output stream.

The output is:

Current time is Wed Aug 20 17:53:49 2014

See also

• Year 2038 problem