[tz] Pre-1970 data

Stephen Colebourne scolebourne at joda.org
Sun Nov 7 17:23:27 UTC 2021

On Fri, 5 Nov 2021 at 04:17, Brian Park <brian at xparks.net> wrote:
> * Descriptive: Paul wants to describe the timezones of the world without regard to how those time zones were created, and merge them into the smallest set that can generate the timekeeping rules. I can see that in this view, merging timezones from different countries into the same equivalence class is reasonable.

The minimalist view espoused by Paul is, IMO, perfectly rationale if,
and only if:
a) there is no pre-1970 history associated with each abstract region
b) the abstract regions have names that don't imply national
boundaries/limits on their scope

Merging without these two things being true merely results in a horrible mess.

There is a perfectly viable solution to the problem if maintenance of
post-1970 timezones was moved to a different repo along the lines
above. This repo could then import the post-1970 definitions and unite
them with the pre-1970 ones (with a different volunteer doing that

> * Prescriptive: I think Stephen and others start with the fact that time zones are the creations of political organizations which write the regulations that define the timezones. Those governing bodies are predominantly organized by country in a hierarchical structure. In this view, it does *not* make sense to merge timezones from different countries. This view also implies that the TZ identifiers should reflect the political organizational structure of the world.

I don't think this is really a good summary. All I'm asking for is a
return to the system that was in use up to 2014 or so. I'm asking
because it is what end users expect, it works well, its backwards
compatible, and it models how timezone rules actually work in the real
world, ie. sometimes based on countries and sometimes real entities
the general public are aware of.

I do not want to see a hierarchical structure of country code and
location, like FR/Paris. Examples like Crimea demonstrate why this is
a bad idea, plus ISO codes get reused eventually making them bad
identifiers. The connection between Europe/Paris and ISO code FR tzdb
currently has is IMO at a completely different level, and far less
politically contentious.

> For this to work, I think we need to clarify the semantics of the 'Link' records in the TZ database. As far as I can tell, there are at least 3 different meanings of the Link record:
> 1) Link Canonical Deprecated
>   * Deprecated is an old zone which should no longer be used
> 2) Link Canonical Alternate
>   * alternate spelling or alias, but not deprecated
> 3) Link Canonical Merged
>   * zones which were merged because they have the same rules by chance, but there is no semantic relationship to each other

It is undoubtedly true that there are different meanings of Link.


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