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 functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here
       and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

       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 POSIX.1-2008, Sec-
       tion 4.15, 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 can-
       not be represented, the function shall return the value (time_t)-1 and set errno to indicate the error.

ERRORS

       The mktime() function shall fail if:

       EOVERFLOW
	      The result cannot be represented.

       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(), tzset(), utime()

       The Base Definitions volume of POSIX.1-2008, Section 4.15, Seconds Since the Epoch, <time.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
       ogy  --	Portable  Operating  System  Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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 Stan-
       dard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE
/The Open Group						       2013								MKTIME(3P)