GNU bug report logs - #63349
Bug in date when using UTC/GMT timeszones in the TZ variable

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Eiríkur Hjartarson <eiki <at> inan.is>
To: bug-coreutils <at> gnu.org
Subject: Bug in date when using UTC/GMT timeszones in the TZ variable
Date: Sun, 7 May 2023 13:28:28 +0000

Hi,

I'm on Fedora-38 GNU/Linux and the version string of 'date' is "date 
(GNU coreutils) 9.1".

$ ls -l /etc/localtime
lrwxrwxrwx. 1 root root 40 jan 11  2022 /etc/localtime -> 
../usr/share/zoneinfo/Atlantic/Reykjavik

Now the "bug":

$ TZ=Europe/Riga date --iso-8601=minutes -d "2024-01-01T00:00-05:00"
2024-01-01T07:00+02:00

$ TZ=UTC+2 date --iso-8601=minutes -d "2024-01-01T00:00-05:00"
2023-01-01T03:00-02:00

That is: the first command gives me the time and date in Riga when it's
midnight at new year's eve in New York.

The second command should do the same but instead gives the time in 
Godthab Greenland.

$ TZ=America/Godthab date -d "2024-01-01T00:00-05:00" --iso-8601=minutes
2024-01-01T03:00-02:00

It seems to me that the sign in the timezone variable could be simply 
reversed.

Regards,
-- 
Eiríkur

Message #8 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: Eiríkur Hjartarson via GNU coreutils Bug Reports
 <bug-coreutils <at> gnu.org>
Cc: 63349 <at> debbugs.gnu.org, Eiríkur Hjartarson <eiki <at> inan.is>
Subject: Re: bug#63349: Bug in date when using UTC/GMT timeszones in the TZ
 variable
Date: Sun, 07 May 2023 16:52:17 +0200

On Mai 07 2023, Eiríkur Hjartarson via GNU coreutils Bug Reports wrote:

> Now the "bug":

It's not a bug.

> $ TZ=Europe/Riga date --iso-8601=minutes -d "2024-01-01T00:00-05:00"
> 2024-01-01T07:00+02:00
>
> $ TZ=UTC+2 date --iso-8601=minutes -d "2024-01-01T00:00-05:00"
> 2023-01-01T03:00-02:00
>
> That is: the first command gives me the time and date in Riga when it's
> midnight at new year's eve in New York.
>
> The second command should do the same but instead gives the time in
> Godthab Greenland.

That's not how TZ works.

https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html
says about the offset:

    Indicates the value added to the local time to arrive at Coordinated
    Universal Time. ...  If preceded by a '-', the timezone shall be
    east of the Prime Meridian; otherwise, it shall be west (which may
    be indicated by an optional preceding '+' ).

Thus TZ=UTC+2 means two hours before UTC.

-- 
Andreas Schwab, schwab <at> linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Message #16 received at 63349-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Andreas Schwab <schwab <at> linux-m68k.org>, 63349-done <at> debbugs.gnu.org
Cc: bug-gnulib <at> gnu.org, eiki <at> inan.is
Subject: Re: bug#63349: Bug in date when using UTC/GMT timeszones in the TZ
 variable
Date: Sun, 7 May 2023 12:36:48 -0400

[Message part 1 (text/plain, inline)]

On 5/7/23 07:52, Andreas Schwab wrote:
> Thus TZ=UTC+2 means two hours before UTC.


Yes, and this mistake seems to be common enough that I installed the 
attached patch into Gnulib, so that it'll propagate into the Coreutils 
manual, which should help people who read the 'date' documentation 
(admittedly only a subset of 'date' users).

[0001-Warn-against-bogus-TZ-settings.patch (text/x-patch, attachment)]

Message #19 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Eiríkur Hjartarson <eiki <at> inan.is>
To: Andreas Schwab <schwab <at> linux-m68k.org>,
 Eiríkur Hjartarson via GNU coreutils Bug Reports
 <bug-coreutils <at> gnu.org>
Cc: 63349 <at> debbugs.gnu.org
Subject: Re: bug#63349: Bug in date when using UTC/GMT timeszones in the TZ
 variable
Date: Sun, 7 May 2023 16:58:34 +0000

On 7.5.2023 14:52, Andreas Schwab wrote:
> On Mai 07 2023, Eiríkur Hjartarson via GNU coreutils Bug Reports wrote:
> 
>> Now the "bug":
> 
> It's not a bug.

Thanks for the explanation, in my defense, I did read the date info page 
and the FAQ at https://www.gnu.org/software/coreutils/faq/coreutils-faq.html
.

Obviously I missed the reference to opengroup.

Regards,
-- 
Eiríkur

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