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Synopsis:
    #include <time.h>
    time_t mktime( struct tm *timeptr );

    struct  tm {
      int tm_sec;   /* seconds after the minute -- [0,61] */
      int tm_min;   /* minutes after the hour   -- [0,59] */
      int tm_hour;  /* hours after midnight     -- [0,23] */
      int tm_mday;  /* day of the month         -- [1,31] */
      int tm_mon;   /* months since January     -- [0,11] */
      int tm_year;  /* years since 1900                   */
      int tm_wday;  /* days since Sunday        -- [0,6]  */
      int tm_yday;  /* days since January 1     -- [0,365]*/
      int tm_isdst; /* Daylight Savings Time flag */
    };

Description:
    The  mktime function converts the local time information in the
    structure pointed to by timeptr into a calendar time (Coordinated
    Universal Time) with the same encoding used by the  time function.  The
    original values of the fields  tm_sec,  tm_min,  tm_hour,  tm_mday, and
     tm_mon are not restricted to ranges described for  struct tm.  If these
    fields are not in their proper ranges, they are adjusted so that they
    are in the proper ranges.  Values for the fields  tm_wday and  tm_yday
    are computed after all the other fields have been adjusted.

    If the original value of  tm_isdst is negative, this field is computed
    also.  Otherwise, a value of 0 is treated as "daylight savings time is
    not in effect" and a positive value is treated as "daylight savings time
    is in effect".

    Whenever mktime is called, the  tzset function is also called.

Returns:
    The  mktime function returns the converted calendar time.

See Also:
    asctime Functions, clock, ctime Functions, difftime, gmtime Functions, localtime Functions, strftime, time,
    tzset

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

    static const char *week_day[] = {
        "Sunday", "Monday", "Tuesday", "Wednesday",
        "Thursday", "Friday", "Saturday"
    };

    void main()
      {
        struct tm new_year;

        new_year.tm_year  = 2001 - 1900;
        new_year.tm_mon   = 0;
        new_year.tm_mday  = 1;
        new_year.tm_hour  = 0;
        new_year.tm_min   = 0;
        new_year.tm_sec   = 0;
        new_year.tm_isdst = 0;
        mktime( &new_year );
        printf( "The next century begins on a %s\n",
                 week_day[ new_year.tm_wday ] );
      }

    produces the following:

    The next century begins on a Monday

Classification:
    ANSI

Systems:
    All