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 .