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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 dif-
       fer (consult 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, Environ-
       ment Variables.

       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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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                            TZSET(3P)