GNU bug report logs - #9614
date: warn on invalid TZ string (was: date ignoring wrong

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From: Pádraig Brady <P <at> draigBrady.com>
To: Sandro Santilli <strk <at> keybit.net>
Cc: 9614 <at> debbugs.gnu.org
Subject: bug#9614: date ignoring wrong TZ values
Date: Tue, 27 Sep 2011 19:19:12 +0100

On 09/27/2011 03:09 PM, Sandro Santilli wrote:
> I've been puzzled by date(1) giving weird results
> when setting TZ to values unknown by zoneinfo.
> 
> As far as:
> 
>  $ TZ=Fake date
>  Tue Sep 27 14:06:32 Fake 2011

Yes, that is per POSIX.
One can specify info about the timezone in TZ
like TZ="Fake+6", so one couldn't start warning about that.

> It would be more helpful if the command raised an error 
> or warning about "unknown" timezones rather than giving
> random dates.
> 
> It's particularly anonying when the same TZ _reported_
> by the command isn't recognized in input:
> 
>   $ date
>   Tue Sep 27 16:08:13 CEST 2011
> 
>   $ TZ=CEST date
>   Tue Sep 27 14:08:13 CEST 2011
> 
> Thanks for making a clock available for everyone, btw :)

Wow you learn something everyday.
I thought the TZ=XYZ was just treated as UTC+0
to allow one to specify TZ=XYZ+4 etc. as
an offset from UTC.

But in fact some TZ values are matched,
as can be seen for CET here on my system:

$ TZ=CEST date
Tue Sep 27 18:03:05 CEST 2011
$ TZ=CET date
Tue Sep 27 20:03:09 CEST 2011
$ date
Tue Sep 27 19:03:17 IST 2011

There are a few three letter codes on my
system at /usr/share/zoneinfo/
(maybe these are the only non ambiguous ones?)

Hmm, how about we warn if an unmatched code (without a /)
is specified, without any other info like UTC offset etc.?

cheers,
Pádraig.

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