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 (consult the correspond-
       ing 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 com-
       ponents of the structure are ignored, and the original values of the other components  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 seasonal 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 determined.

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 Definitions 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 Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (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.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								MKTIME(3P)