[tz] Issues with pre-1970 information in TZDB

[Robert Elz]

    Date:        Fri, 24 Sep 2021 14:10:29 -0700
    From:        Paul Eggert <eggert at cs.ucla.edu>
    Message-ID:  <5189c80f-7242-d8dd-8f87-6e25c714283a at cs.ucla.edu>

  | I've tried to cover that topic in other emails but have no doubt missed 
  | some points. But here's another point: the set of political units with 
  | these powers have changed with time

Yes.

  | so do we allow new Zones only 
  | political units with these powers since 1970?

For zones that have never existed (are not in the main files, or backzone)
only for authorities that exist at the time of asking.

Once created (and stable, ie: we can fix typos, and other errors, soon
after creation - certainly any time between when created in the source db
and the next release) zones should never be removed.   Never.
Moving to backzone is removed for this purpose.

  | Or if we reject the other 
  | political units then what's our justification for that?

The point is to avoid authorities from feeling the need to fiddle
their timezones just to qualify for a zone.   Only current authorities
with the appropriate actual capacity can do that, nothing that no
longer exists, and nothing that is merely claimimg power ("I should be
in charge") but actually has none.

  | Unfortunately it would not work, for reasons I discussed a few minutes 
  | ago (not yet in the tzdb archive, but I hope you can find it).

I have seen it.   I don't believe them.

  | It wouldn't be either. It would be on the scale that we've done in 
  | previous releases. Typically, we'd change about 10 Zones to Links (and 
  | move the resulting data to 'backzone' so it wouldn't get lost). This 
  | worked well in practice.

Please, don't.   Just don't.   Avoid any provocation for now, and do exactly
2021a plus updates for Samoa and Jordan (and anything else similar that
exists).  No zone merges at all.   None of that is urgent.   They can all
wait for a later update (or perhaps, never happen at all).

kre