Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!lavaca.uh.edu!menudo.uh.edu!st12a
From: st12a@menudo.uh.edu (richard henderson~)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Time Zones: A Plea for Standards?
Message-ID: <1991Apr15.155026.20777@menudo.uh.edu>
Date: 15 Apr 91 15:50:26 GMT
References: <1991Apr15.200244.7775@cc.curtin.edu.au>
Organization: University of Houston
Lines: 60

In article <1991Apr15.200244.7775@cc.curtin.edu.au> nmurrayr@cc.curtin.edu.au (Ron Murray) writes:
>
>   While it's nice to see that programmers are beginning to realise that there
>IS life outside their own country / timezone, it would be nice if they could
>find some way of specifying this timezone without using a TZ environment
>variable.
>   Perhaps I should explain. My interests are fairly wide-ranging, and they
>include astronomy and various messaging systems. It seems, however, that
>every man and his dog gets the brilliant idea of specifying the user's
>time zone with an environment variable called. for some reason, "TZ". Even
>that wouldn't be quite so bad if they all wanted it in the same format, but
>some programs seem to want a three-letter code (e.g. "WST"), some want this
>code but with a displacement from UTC added (and barf if it happens to be
>negative!), and some are even worse. The result is that I can't have more
>than one of these programs on my system at the same time, or one or more of
>them gets upset, or more likely insists that the local time is 4 am when the
>sun is shining outside.

There _is_ a standard format for the TZ environment variable out there.
There has been one for unix systems since the early 80s (I think).  Now why
people think they hav eto re-invent their own is another story.

Here is the  "official" format for this variable taken from MINIX POSIX source:

* Time zones (TZ) are given as strings of the form (spaces only for clarity)
*
*    Std Offset [Dst [Offset] [,Startdate[/Time], Enddate[/Time]]]
*
* where:
* Std and Dst three or more bytes that are the designation for the standard
*             (std) or summer (dst) time zone. Only std is required; if dst
*             is missing, then summer time doen not apply in this locale.
*
* Offset and  Indicates the value one must add to the local time to arrive
* Time        at Coordinated Universal Time. The offset has the form
*                hh[:mm[:ss]]
*             The hours shall be required and may be a single digit. If no
*             offset follows dst, summer time is assumed to be one hour ahead
*             of standard time. If preceded by a "-", the time zone shall be
*             east of the Prime meridian; otherwise it shall be west. Default
*             DST offset will be 1 hour, default switch Time will be 02:00:00
*
* date        The format of the date shall be one of the following:
*             Jn      Julian day (1 <= n <= 365)
*                     leapdays are NOT counted, so March 1 is always day 60
*             n       Zero-based Julian day (0 <= n <= 365)
*                     leapdays are counted, so March 1 is day 61 in leapyears
*             Mm.n.d  The d-th day (0<=d<=6) of week n (1 <=n<=5) of month
*                     m (1<=m<=12), where week 5 means 'the last d day in
*                     month m' which may occur in either the fourth or
*                     fifth week. Week 1 is the first week in which d'th
*                     day occurs. Day zero is sunday.
*
* See for more explanations on the TZ definition the IEEE Std 1003.1-1988
* Posix Standard, paragraphs 8.1.1 "Extensions to Time Functions" on 142-143.

--------
richard~
st12a@menudo.uh.edu
richard@stat.tamu.edu