[tz] Vanguard vs. "main" vs. rearguard

[Paul Eggert]

On 6/9/21 9:43 AM, Neil Fuller wrote:

> Because Android typically doesn't get to
> update code for TZDB updates, only data, it will stick with the "fat"
> format for existing devices.

I can understand Android doing that, given old apps that read TZif files 
directly and that predate RFC 8536 or have bugs related to RFC 8536. I 
expect it'll take many years for RFC 8536 to proliferate.

> e.g. if two projects want country-specific zone IDs, and they don't come
> from TZDB, then there's a risk of one of them "inventing" (should the need
> arise) Europe/Glasgow as "the zone for Scotland", and another inventing
> Europe/Edinburgh to fill the same role.

Yes, that's very much a concern. And it's not just Scotland: it could 
happen with the Oduduwa Republic or any number of other plausible future 
countries created by political disputes. This is a primary motivation 
for the guidelines not requiring a separate Zone per country.