[tz] Some thoughts about the way forward

[Paul Eggert]

On 9/24/21 7:32 PM, Deborah Goldsmith wrote:
> AFAIK Apple software doesn’t have a problem with length, just the pattern, which currently follows the spec.

Yes, thanks for bringing that up. We should consider that in any version 
number variant we might want to use in the near future.

If I read the spec correctly, the pattern Apple uses should be 
equivalent to the POSIX extended regular expression '[0-9]{4}z*[a-z]' in 
the C locale. Am I right about Apple's pattern?

Also, does Apple software insist that version numbers must be in strict 
order? For example, does it require that the version after '2021zz' must 
be either '2021zza' or a version Ya where Y is a four-digit year greater 
than 2021? or could the next version after '2021zz' be anything matched 
by the abovementioned pattern? The spec is silent on this subject.

> If you propose changing it, there needs to be a new spec, and a considerable period of time (preferably a year) to adjust to it.

Yes, quite so. Plus, the above details should be nailed down. (And the 
spec should be extended so that it clearly allows year numbers greater 
than 9999 - even though there should be *plenty* of time before that 
particular flexibility is needed....)