timezone(4)

NAME
     timezone - set default system time zone

SYNOPSIS
     /etc/TIMEZONE

DESCRIPTION
     This file sets the time zone environmental variable TZ.

     This file is read by init(1) after system boot up and all subsequent
     processes inherit TZ in their environment.  Other variables than TZ may
     also be set in this file, for programs that are run from init.  Some
     programs started by init reset all or part their environment, and
     therefore these variables may not be seen by all programs.  The form of
     the variables is

               VARIABLE=value

     Lines that are too long are ignored; in practice this is not a problem.

     The syntax of TZ can be described as follows:

     TZ             ->         zone
                              | zone signed_time
                              | zone signed_time zone
                              | zone signed_time zone dst
     zone           ->         letter letter letter
     signed_time         ->         sign time
                              | time
     time           ->         hour
                              | hour : minute
                              | hour : minute : second
     dst            ->         signed_time
                              | signed_time , dst_date , dst_date
                              | , dst_date , dst_date
     dst_date            ->         julian
                              | julian / time
     letter              ->          a | A | b | B | ... | z | Z
     hour                ->          00 | 01 | ... | 23
     minute              ->          00 | 01 | ... | 59
     second              ->          00 | 01 | ... | 59
     julian              ->          001 | 002 | ...| 366
     sign           ->          - | +

EXAMPLES
     The contents of /etc/TIMEZONE corresponding to the simple example below
     could be

          #    Time Zone
          TZ=EST5EDT

     A simple setting for New Jersey could be

          TZ=EST5EDT

     where EST is the abbreviation for the main time zone, 5 is the
     difference, in hours, between GMT (Greenwich Mean Time) and the main time
     zone, and EDT is the abbreviation for the alternate time zone.

     The most complex representation of the same setting, for the year 1986,
     is

          TZ=EST5:00:00EDT4:00:00,117/2:00:00,299/2:00:00

     where EST is the abbreviation for the main time zone, 5:00:00 is the
     difference, in hours, minutes, and seconds between GMT and the main time
     zone, EDT is the abbreviation for the alternate time zone, 4:00:00 is the
     difference, in hours, minutes, and seconds between GMT and the alternate
     time zone, 117 is the number of the day of the year (Julian day) when the
     alternate time zone will take effect, 2:00:00 is the number of hours,
     minutes, and seconds past midnight when the alternate time zone will take
     effect, 299 is the number of the day of the year when the alternate time
     zone will end, and 2:00:00 is the number of hours, minutes, and seconds
     past midnight when the alternate time zone will end.

     A southern hemisphere setting such as the Cook Islands could be

          TZ=KDT9:30KST10:00,64/5:00,303/20:00

     This setting means that KDT is the abbreviation for the main time zone,
     KST is the abbreviation for the alternate time zone, KDT is 9 hours and
     30 minutes later than GMT, KST is 10 hours later than GMT, the starting
     date of KST is the 64th day at 5 AM, and the ending date of KST is the
     303rd day at 8 PM.

     Starting and ending times are relative to the alternate time zone.  If
     the alternate time zone start and end dates and the time are not
     provided, the days for the United States that year will be used and the
     time will be 2 AM.  If the start and end dates are provided but the time
     is not provided, the time will be midnight.

NOTES
     The system administrator must change the Julian start and end days
     annually if the longer form of the TZ variable is used.

     Setting the time during the interval of change from the main time zone to
     the alternate time zone or vice versa can produce unpredictable results.

     Timezone specifications under the IRIX 4 operating system used a ";" to
     separate the dst field from the dst_date field.  In conformance with the
     X/Open XPG4 standard, this is no longer legal, and a "," must be used in
     place of the ";".
SEE ALSO
     environ(5), ctime(3C)