[tz] [PATCH] Update Crimea country codes in line with UN A/RES/73/263

[Paul Eggert]

On 3/25/21 5:46 PM, Dimitri John Ledkov via tz wrote:
> I'm not quite sure what it means to have "CZ,SK" dual
> code for Europe/Prague.

It means that Europe/Prague covers some territory in both CZ (Czech 
Republic) and SK (Slovakia). This is mentioned in the comments at the 
start of zone1970.tab.

> is it just an oversight that Europe/Bratislava is not listed in the
> zone1970.tab file

No, it's intended. The Europe/Bratislava link is present for backward 
compatibility; it's no longer really needed for tzdb settings since 
Slovakia's clocks have agreed with Europe/Prague's since 1970.

> It would be more helpful to return CS code for
> years 1918–1939 and 1945–1992

Not really as that wouldn't be historically accurate, and even if it 
were accurate it would cause more political hassles than we already have 
(people care a lot about history for some reason :-).

> zone1970 is not helpful, especially since it's
> alphabetical sort 

Is this referring to some existing Ubuntu-based software that uses 
zone.tab and that requires alphabetical sorting? I'd be interested to 
know what software has this problem. It might be possible to work around 
problems in this area, but I'd need to know what the problems actually are.

> will not yield appropriate country code for
> Europe/Simferopol pre/post 2014 time periods

That's OK, as zone1970.tab is not a historical database. It's intended 
only for people who are setting their timezones today.

> Are there plans to add a new zone.tab format that provides UNTIL field?

No, for the reasons mentioned above.

In hindsight the zone.tab file was a mistake because it inspires too 
many political controversies. zone1970.tab is somewhat better, but even 
it goes beyond what a timezone database needs to do.

These two files were intended only as aids to user interfaces to 
selecting timezones. Modern timezone-selection user interfaces typically 
use boundaries[1] rather than these files, so perhaps someday we can 
remove both of them. Any continuing political controversy about them 
will likely accelerate the process of their removal.

[1] https://data.iana.org/time-zones/tz-link.html#boundaries