TZSET(3P)                                           POSIX Programmer's Manual                                          TZSET(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
       daylight, timezone, tzname, tzset - set timezone conversion information

SYNOPSIS
       #include <time.h>



       extern int daylight;
       extern long timezone;


       extern char *tzname[2];
       void tzset(void);


DESCRIPTION
       The  tzset()  function  shall  use  the  value  of the environment variable TZ to set time conversion information used by
       ctime(), localtime(), mktime(), and strftime() . If TZ is absent from  the  environment,  implementation-defined  default
       timezone information shall be used.

       The tzset() function shall set the external variable tzname as follows:


              tzname[0] = "std";
              tzname[1] = "dst";

       where  std  and dst are as described in the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment Vari-
       ables.

       The tzset() function also shall set the external variable daylight to 0 if Daylight Savings Time conversions should never
       be  applied  for the timezone in use; otherwise, non-zero. The external variable timezone shall be set to the difference,
       in seconds, between Coordinated Universal Time (UTC) and local standard time.

RETURN VALUE
       The tzset() function shall not return a value.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       Example TZ variables and their timezone differences are given in the table below:

                                                         TZ          timezone
                                                         EST5EDT     5*60*60
                                                         GMT0        0*60*60
                                                         JST-9       -9*60*60
                                                         MET-1MEST   -1*60*60
                                                         MST7MDT     7*60*60
                                                         PST8PDT     8*60*60

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       ctime(), localtime(), mktime(), strftime(), the Base Definitions volume of IEEE Std 1003.1-2001, Chapter  8,  Environment
       Variables, <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                                                     TZSET(3P)