[tz] Issues with pre-1970 information in TZDB

[Paul Eggert]

On 9/22/21 12:51 PM, Tom Lane via tz wrote:
>  From my perspective, it'd have been better or at least more honest
> if the moved zones had disappeared from the TZif tree altogether.

That's what we did long ago, but as I vaguely recall there was 
resistance to removing data. Hence 'backzone', which is not part of the 
default database, and which contains data that's unnecessary according 
to the current guidelines, data that are often of lower quality.

The current disagreement is mostly over whether part of 'backzone' is 
necessary. There is an argument that some (but not all) of the 
'backzone' data is necessary in order to accommodate certain political 
concerns, and that the guidelines should be altered to say that these 
political concerns are enough to justify Zones that would not otherwise 
be needed. I'm skeptical of that argument, partly because that means 
there'll be more low-quality data in the database, partly because it 
means more work for us and for our users for essentially zero benefit, 
and partly because the more we entangle tzdb with politics the more time 
we'll waste in political debates.