MKTIME(3P)                                          POSIX Programmer's Manual                                         MKTIME(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       mktime - convert broken-down time into time since the Epoch

SYNOPSIS
       #include <time.h>

       time_t mktime(struct tm *timeptr);


DESCRIPTION
       The  mktime()  function  shall  convert  the  broken-down  time,  expressed as local time, in the structure pointed to by
       timeptr, into a time since the Epoch value with the same encoding as that of the values returned by time(). The  original
       values  of  the  tm_wday and tm_yday components of the structure are ignored, and the original values of the other compo-
       nents are not restricted to the ranges described in <time.h>.

       A positive or 0 value for tm_isdst shall cause mktime() to presume initially that Daylight Savings Time, respectively, is
       or  is  not  in effect for the specified time. A negative value for tm_isdst shall cause mktime() to attempt to determine
       whether Daylight Savings Time is in effect for the specified time.

       Local timezone information shall be set as though mktime() called tzset().

       The relationship between the tm structure (defined in the <time.h> header) and the time in seconds  since  the  Epoch  is
       that  the result shall be as specified in the expression given in the definition of seconds since the Epoch (see the Base
       Definitions volume of IEEE Std 1003.1-2001, Section 4.14, Seconds Since the Epoch) corrected for timezone  and  any  sea-
       sonal time adjustments, where the names in the structure and in the expression correspond.

       Upon successful completion, the values of the tm_wday and tm_yday components of the structure shall be set appropriately,
       and the other components are set to represent the specified time since the Epoch, but with their  values  forced  to  the
       ranges  indicated  in the <time.h> entry; the final value of tm_mday shall not be set until tm_mon and tm_year are deter-
       mined.

RETURN VALUE
       The mktime() function shall return the specified time since the Epoch encoded as a value of  type  time_t.  If  the  time
       since the Epoch cannot be represented, the function shall return the value (time_t)-1.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       What day of the week is July 4, 2001?


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


              struct tm time_str;


              char daybuf[20];


              int main(void)
              {
                  time_str.tm_year = 2001 - 1900;
                  time_str.tm_mon = 7 - 1;
                  time_str.tm_mday = 4;
                  time_str.tm_hour = 0;
                  time_str.tm_min = 0;
                  time_str.tm_sec = 1;
                  time_str.tm_isdst = -1;
                  if (mktime(&time_str) == -1)
                      (void)puts("-unknown-");
                  else {
                      (void)strftime(daybuf, sizeof(daybuf), "%A", &time_str);
                      (void)puts(daybuf);
                  }
                  return 0;
              }

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       asctime(), clock(), ctime(), difftime(), gmtime(), localtime(), strftime(), strptime(), time(), utime(), the Base Defini-
       tions volume of IEEE Std 1003.1-2001, <time.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    MKTIME(3P)