C Reference function mktime()

Usage of mktime():

time_t mktime ( struct tm * ptr_time );

Parameters:

The pointer ptr_time points to a tm structure that contains a calendar time, which in turn is broken down into its components.

Return Value:

A time_t value corresponding to the calendar time passed as argument.
If an error occurs then the function mktime() returns a -1 value.

Explanation:

The contents of the tm structure is interpret by the mktime function as a calendar time expressed in local time.
This calendar time is then used to change the values of the members of the ptr_time. The result will be returned as an object of the type time_t.

The original values of the members tm_wday and tm_yday of timeptr are ignored.

Note: the ranges of values for the rest of its members are not restricted to their normal values.

The object pointed by ptr_time is modified, setting the tm_wday and tm_yday to their appropriate values.
It then modifies the other members, if necessary, to values within the normal range representing the specified time.

Source code example of mktime():

	#include <stdio.h>
	#include <time.h>

	int main(void)
	{
		struct tm time_info;
		time_t time_raw_format;

		time_info.tm_year = 2008-1900;
		time_info.tm_mon = 0;
		time_info.tm_mday = 1;
		time_info.tm_hour = 0;
		time_info.tm_min = 0;
		time_info.tm_sec = 1;
		time_info.tm_isdst = 0;

		time_raw_format = mktime(&time_info);
		printf(ctime(&time_raw_format));
		return 0;
	}

Output example of the program above:

	Tue Jan  1 00:00:01 2008