[Bug 2017999] Re: tzdata 2023c-0ubuntu0.22.04.1 might have some inconsistency

[Robie Basak]

This upload proposes to remove some of the options in
debian/tzdata.templates. So what happens if a user has configured
deployment automation to use particular debconf options that will now
disappear? The changelog says "It removes following time zones from
debconf and updates them on upgrades again" but what about the
reproducibility of previous behaviour on redeployments?

This would apply to:

America/
  Argentina/ComodRivadavia
  Rosario
Asia/
  Hanoi
Europe/
  Uzhgorod
  Zaporozhye
Pacific/
  Enderbury

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https://bugs.launchpad.net/bugs/2017999

Title:
  tzdata 2023c-0ubuntu0.22.04.1 might have some inconsistency

Status in python-tz package in Ubuntu:
  Fix Released
Status in tzdata package in Ubuntu:
  Fix Released
Status in python-tz source package in Focal:
  Invalid
Status in tzdata source package in Focal:
  New
Status in python-tz source package in Jammy:
  Invalid
Status in tzdata source package in Jammy:
  New
Status in python-tz source package in Kinetic:
  Invalid
Status in tzdata source package in Kinetic:
  New
Status in python-tz source package in Lunar:
  Fix Committed
Status in tzdata source package in Lunar:
  New

Bug description:
  [ Impact ]

  Recent updates have been using `PACKRATDATA=backzone` in order to add
  all out-of-scope lower-quality pre-1970 data back that existed in
  earlier tzadata releases (see bug #2003797). However it also leads to
  time zones like America/Ensenada, Atlantic/Jan_Mayen, Europe/Tiraspol,
  and Pacific/Enderbury to change:

  compared to 2023c-0ubuntu0.22.04.0
  - America/Ensenada->only dst changes until 2022 are shown
  - Atlantic/Jan_Mayen->now valid data is shown
  - Europe/Tiraspol->only dst changes until 2010 are shown

  [ Test Plan ]

  Add an autopkgtest test case for post-1970 symlink consistency: Check
  that the timezones for today and in half a year (= to cover DST
  changes) do not change compared to building them without
  `PACKRATDATA=backzone`.

  The mentioned timezones that differed can also be tested manually.
  Running following commands should have the same output (the output
  mentioned here is from tzdata 2023c-0ubuntu0.22.04.1):

  ```
  $ TZ=America/Ensenada date -d "2023-04-28 13:49 Z"
  Fri Apr 28 05:49:00 PST 2023
  $ TZ=Atlantic/Jan_Mayen date -d "2023-04-28 13:49 Z"
  Fri Apr 28 12:49:00 -01 2023
  $ TZ=Europe/Tiraspol date -d "2023-04-28 13:49 Z"
  Fri Apr 28 16:49:00 MSK 2023
  ```

  [ Where problems could occur ]

  Timezone data could be wrong. Systems with incorrect timezone set may
  observe unexpected time shift when updating the package.

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