Tom Lane via tz <tz@iana.org> wrote on Sun, 6 Jun 2021 at 13:31:06 EDT in <655997.1623000666@sss.pgh.pa.us>:
I had a further thought about this: if we want to have both of these principles (zone-per-country and stability of old data), then it would make sense to insist that we don't create new per-country zones until someone has done the research to fill in plausible old data back to the LMT era for the proposed zone name.
I don't think this is correct or fair. It's not correct because if there is a newly established zone (per-country or otherwise), early adopters of that zone can tolerate some flux in the data. It's not as if we're coming into an established zone with a lot of dependancies and expectations of stability. If the new zone goes in and today and the historical data comes a year later, that's probably OK. Not ideal, but OK. For sure we'd want to minimize adding it in fits and starts. I don't think it's fair because the tz database needs to turn on a dime to reflect political changes that happen on rapid timescales. If a zone into two countries (whether by one of two previously-aligned countries changing their time zone rules, or by other political or even military mechanism) overnight, we need to push a new release out ASAP, we can't say, "oh, sorry, you can't have working time on your computers, we have to research the history, just suffer along for 6 months." -- jhawk@alum.mit.edu John Hawkinson