Add note to Debconf template about unintuitive inverted Etc/GMT offsets

[Tarmo Sergo]

Looks like GMT[+-}<number> timezones have signs swapped.

My local timezone is Europe/Tallinn

When timezone is set to "Europe/Tallinn", everything is ok:
# dpkg-reconfigure tzdata -> Europe/Tallinn
# date
Tue Jun 3 14:34:21 EEST 2014

# date +%z
+0300

# date -u
Tue Jun 3 11:34:59 UTC 2014

I need to set timezone to GMT+2, to avoid dailight savings time.
When I set timezone to "GMT+2", things fall apart. Timezone is shown GMT+2/GMT-2. Clock is set to GMT-2.
# dpkg-reconfigure tzdata -> Etc/GMT+2

# date
Tue Jun 3 09:36:21 GMT+2 2014

# date +%z
-0200

# date -u
Tue Jun 3 11:37:43 UTC 2014

When I set timezone to "GMT-2", then it's turned around. Timezone is shown GMT-2/GMT+2. Clock is set to GMT+2.
#dpkg-reconfigure tzdata -> Etc/GMT-2

# date
Tue Jun 3 13:39:35 GMT-2 2014

# date +%z
+0200

# date -u
Tue Jun 3 11:39:56 UTC 2014

# lsb_release -rd
Description: Ubuntu 12.04.4 LTS
Release: 12.04

# apt-cache policy tzdata
tzdata:
  Installed: 2014c-0ubuntu0.12.04
  Candidate: 2014c-0ubuntu0.12.04
  Version table:
 *** 2014c-0ubuntu0.12.04 0
        500 http://ee.archive.ubuntu.com/ubuntu/ precise-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2012e-0ubuntu0.12.04.1 0
        500 http://security.ubuntu.com/ubuntu/ precise-security/main amd64 Packages
     2012b-1 0
        500 http://ee.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages

# apt-get update
# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1325949/+editstatus and add the package name in the text box next to the word Package.

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[Brian Murray (brian-murray)]

The same bug occurs when using tzdata version 2012b-1, so it is not a regression.

[Paul Eggert (eggert-gnu)]

Please change this to WONTFIX. The confusing entries are part of the upstream tz database, and they've been there 20 years or so. They are present only for backward-compatibility reasons for decades-old usage, which are discussed in the "etcetera" file of the tzdata distribution. The confusing entries should not be used by new applications, and are not likely to change in the future (unless they're simply removed entirely).

[Ben Humpert (an3k)]

Please do not change to WONTFIX.

# We use POSIX-style signs in the Zone names and the output abbreviations,
# even though this is the opposite of what many people expect.
# POSIX has positive signs west of Greenwich, but many people expect
# positive signs east of Greenwich. For example, TZ='Etc/GMT+4' uses
# the abbreviation "GMT+4" and corresponds to 4 hours behind UT
# (i.e. west of Greenwich) even though many people would expect it to
# mean 4 hours ahead of UT (i.e. east of Greenwich).

The thing is, it is not about "what many people expect". It is about the international standard and if POSIX does not handle it correctly POSIX has to be changed. POSIX does not follow the international standard which clearly says XXX+1 means one hour ahead of XXX. This is definied in international ISO norm, european EN norm and german DIN norm and there are definitely many other countries using the well-known ISO norm too.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Adam Conrad (adconrad)]

I have no intention of inventing a time machine and "fixing" POSIX. Please don't use the Etc/* timezones if the inverted offsets confuse you, there are many other ways to get at the timezones in human-friendly and less mind-bending ways.

[Adam Conrad (adconrad)]

On second thought, reopening this bug as a wishlist to add a note to the Debconf template to explain the inverted nature of the Etc/GMT offsets.

[Ben Humpert (an3k)]

So how to set timezone to Europe/Berlin (GMT+1) but without DST? I haven't found a tzdata setting allowing this.

[Benjamin Drung (bdrung)]

I reported this unintuitive behavior to upstream: https://mm.icann.org/pipermail/tz/2023-April/032897.html

[Benjamin Drung (bdrung)]

Result from the upstream discussion: We will update debconf question with an explanation: https://mm.icann.org/pipermail/tz/2023-May/032942.html

[Launchpad Janitor (janitor)]

This bug was fixed in the package tzdata - 2023c-4exp1ubuntu1

---------------
tzdata (2023c-4exp1ubuntu1) mantic; urgency=medium

  * Merge with Debian experimental. Remaining changes:
    - Ship 2023c ICU timezone data which are utilized by PHP in tzdata-icu
    - Add autopkgtest test case for ICU timezone data
    - Do not rename NEWS into changelog.gz, this fixes a build failure on
      moment-timezone.js
    - Point Vcs-Browser/Git to Launchpad
    - generate_debconf_templates: Work around AttributeError on icu import

tzdata (2023c-4exp1) experimental; urgency=medium

  * Drop /usr/share/zoneinfo/posix (identical to /usr/share/zoneinfo)
    (LP: #2008076)
  * Split right/* timezones into separate tzdata-legacy package (LP: #2008076)
  * Drop providing tzdata-bookworm from tzdata

tzdata (2023c-4) unstable; urgency=medium

  * Sort timezones naturally in debconf
  * Add explanation for plus/minus used by Etc/GMT timezones
    (Closes: #540305, LP: #1325949)
  * Build tzdata with PACKRATLIST=zone.tab. In combination with
    PACKRATDATA=backzone (which is used since 2022g-3), time zones that differ
    pre-1970 and had been resurrected will not incur changes to data from 1970
    on. This also removes Asia/Hanoi again. (LP: #2017999)
  * Update Croatian debconf translation. Thanks to Tomislav Krznar.

tzdata (2023c-3) unstable; urgency=medium

  * test_timezone_conversions: Print all failures before failing
  * Add Romanian debconf translation. Thanks to Remus-Gabriel Chelu
    (Closes: #1034094)
  * Add Language metadata to all debconf translation files
  * Convert Pacific/Ponape to Pacific/Pohnpei on upgrade
  * Convert Asia/Ujung_Pandang to Asia/Makassar on upgrade
  * Convert Pacific/Truk to Pacific/Chuuk on upgrade
  * Fix or drop wrong translations
  * Check debconf translation files for inconsistencies
  * Fix German translation of Christmas and Easter Island

 -- Benjamin Drung <email address hidden> Wed, 10 May 2023 00:26:05 +0200