On Sep 24, 2021, at 1:27 PM, Paul Eggert via tz <tz@iana.org> wrote:
We can't have a free-for-all in which anyone can add a Zone for (say) Kosciusko County, Indiana to the primary database on the grounds that it differed from Indianapolis back in 1906. Even covering Indiana alone would require hundreds of Zones, the data would be practically impossible to verify, and the overall utility to end users would be negative (due to the resulting complication and confusion).
And if all those Zones were added (this is, as I understand it, *adding* Zones, *not* converting Links to Zones), would Apple, OpenStreetMaps, Ubuntu (assuming they don't just use OpenStreetMaps and the tz shape files generated from them), etc. start using them? Apple might be using some backzone entries *now*, but I'm not sure they'd sign up to set up their city list and map information to handle all of them. Perhaps a policy of, at minimum, "we will not create any new Zones for pre-1970 differences", if that's not *already* a firm policy, would make it clearer that tzdb isn't "the" time zone database for all of time, it's only going to be "the" time zone database for 1970 and beyond, and if anybody needs correct information on time offsets prior to 1970 for all locations in a given area, they're welcome to develop it and maintain it themselves.