<ctime>
time_t mktime ( struct tm * timeptr );
Convert tm structure to time_t
Interprets the contents of the tm structure pointed by timeptr as a calendar time expressed in local time. This calendar time is used to adjust the values of the members of timeptr accordingly and returned as an object of type time_t.
The original values of the members tm_wday and tm_yday of timeptr are ignored, and the ranges of values for the rest of its members are not restricted to their normal values (like tm_mday being between 1 and 31).
The object pointed by timeptr is modified, setting the tm_wday and tm_yday to their appropiate values, and modifying the other members as necessary to values within the normal range representing the specified time.
Parameters
- timeptr
- Pointer to a tm structure that contains a calendar time broken down into its components (see tm).
Return Value
A time_t value corresponding to the calendar time passed as argument.
On error, a -1 value is returned.
Example
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/* mktime example: weekday calculator */
#include <stdio.h>
#include <time.h>
int main ()
{
time_t rawtime;
struct tm * timeinfo;
int year, month ,day;
char * weekday[] = { "Sunday", "Monday",
"Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"};
/* prompt user for date */
printf ("Enter year: "); scanf ("%d",&year);
printf ("Enter month: "); scanf ("%d",&month);
printf ("Enter day: "); scanf ("%d",&day);
/* get current timeinfo and modify it to the user's choice */
time ( &rawtime );
timeinfo = localtime ( &rawtime );
timeinfo->tm_year = year - 1900;
timeinfo->tm_mon = month - 1;
timeinfo->tm_mday = day;
/* call mktime: timeinfo->tm_wday will be set */
mktime ( timeinfo );
printf ("That day is a %s.\n", weekday[timeinfo->tm_wday]);
return 0;
}
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Output:
Enter year: 2000
Enter month: 5
Enter day: 20
That day is a Saturday.
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See also.
| asctime | Convert tm structure to string (function) |
| gmtime | Convert time_t to tm as UTC time (function) |
| localtime | Convert time_t to tm as local time (function) |
| time | Get current time (function) |
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