NAME

     TZ - Time zone environment variable


SYNOPSIS

     TZ=zone[-]offset[dst[offset][,start[/time],end[/time]]]


DESCRIPTION

     The TZ environment variable  tells  functions  such  as  the
     ctime(3)  family  and  programs like date what the time zone
     and daylight saving rule is.  The value of TZ has the  POSIX
     standardized  form  shown in the synopsis.  This form speci-
     fies the zone names, offsets from GMT, and  daylight  saving
     changeover times for at least the current year.

     zone A three or more letter name for the time zone in normal
          (winter) time.

     [-]offset
          A signed time telling the offset of the time zone west-
          wards   from   Greenwich.    The   time  has  the  form
          hh[:mm[:ss]] with a one of two digit hour, and optional
          two digit minutes and seconds.

     dst  The name of the time zone when daylight  saving  is  in
          effect.   It  may  be followed by an offset telling how
          big the clock correction is other than the default of 1
          hour.

     start/time,end/time
          Specifies the start and  end  of  the  daylight  saving
          period.   The start and end fields indicate on what day
          the changeover occurs.  They must be in one of the fol-
          lowing formats:

          Jn   The Julian day n (1 <= n  <=  365)  ignoring  leap
               days, i.e. there is no February 29.

          n    The zero-based Julian day (0 <= n <=  365).   Leap
               days are not ignored.

          Mm.n.d
               This indicates month m, the n-th occurrence of day
               d  (1 <= m <= 12, 1 <= n <= 5, 0 <= d <= 6, 0=Sun-
               day).   The  5-th  occurrence   means   the   last
               occurrence  of  that day in a month.  So M4.1.0 is
               the first Sunday in April, M9.5.0 is the last Sun-
               day in September.

          The time field indicates the time the changeover occurs
          on the given day.



EXAMPLES

     Greenwich Mean Time:

          TZ=GMT0

     Central European Time, 1 hour east from Greenwich,  daylight
     saving  starts  on the last Sunday in March at 2 AM and ends
     on the last Sunday in October at 3 AM:

          TZ='CET-1CEST,M3.5.0/2,M10.5.0/3'

     British time, daylight saving starts and ends  at  the  same
     moment as CET, but in an earlier time zone:

          TZ=GMT0BST,M3.5.0/1,M10.5.0/2

     The eastern european time zones also have the changeovers at
     the same absolute time as British time and CET.

     U.S. Eastern Standard Time, 5  hours  west  from  Greenwich,
     daylight  saving starts on the first Sunday in April at 2 AM
     and ends on the last Sunday in October at 2 AM:

          TZ=EST5EDT,M4.1.0/2,M10.5.0/2

     It shouldn't surprise you that daylight saving in  New  Zea-
     land  is  observed  in the months opposite from the previous
     examples.  It starts on the first Sunday in October at 2  AM
     and ends on the third Sunday in March at 3 AM:

          TZ=NZST-12NZDT,M10.1.0/2,M3.3.0/3


SEE ALSO

     readclock(8), date(1).


BUGS

     You may have noticed that many fields are optional.   Do  no
     omit them, because the defaults are bogus.  If you need day-
     light saving then fully specify the changeovers.

     West is negative, east is positive, ask any sailor.

     Next year's time zone and daylight saving  time  are  deter-
     mined by politicians.


AUTHOR

     Kees J. Bot (kjb@cs.vu.nl)