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 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,
       Standard for Information Technology -- 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                                              TZSET(P)