MKTIME(3C)                           SysV                           MKTIME(3C)



NAME
     mktime - convert broken-down time to calendar time

SYNOPSIS
     #include <time.h>

     time_t mktime(timeptr)
     struct tm *timeptr;

DESCRIPTION
     The mktime function converts the broken-down time, expressed as local
     time, in the type tm structure pointed to by the timeptr parameter, into
     a time since the EPOCH in the same format as that of values returned by
     the time function.  The original values of parameters timeptr->tm_wday
     and timeptr->tm_yday of the structure are ignored, and the original
     values of other members of the structure are not restricted to the ranges
     defined in the time.h header file. The range [0, 61] for structure member
     tm_sec allows for an occasional leap second or double leap second.

     A positive or 0 (zero) value for member tm_isdst tells the mktime
     function whether daylight saving time is in effect.  A negative value for
     tm_isdst tells the mktime function to find out whether daylight saving
     time is in effect for the specified time. Local time-zone information is
     set as though the tzset(3C) function were called.

     On successful completion, values for the timeptr->tm_wday and timeptr-
     >tm_yday members of the structure are set, and the other members are set
     to specified times since the EPOCH, but with their values forced to the
     ranges indicated above; the final value of timeptr->tm_mday is not set
     until the values of members timeptr->tm_mon and timeptr->tm_year are
     determined.

SEE ALSO
     time(2), ctime(3C), difftime(3C).

DIAGNOSTICS
     Upon successful completion, the mktime function returns the specified
     time since the EPOCH written as a value of type time_t .  On error, or
     whenever the time since the EPOCH cannot be represented, this function
     returns the value (time_t)-1.

NOTE
     Parts of this discussion are adapted from ANS X3.159-1989.