[tz] tzdb timezone names/identifiers and links (was: Add new timezone for Hanoi Capital, Vietnam)

Paul Eggert eggert at cs.ucla.edu
Tue Feb 19 16:34:42 UTC 2019

Hans-Joerg Happel wrote:
> So any information on the rationale for the above-quoted rule is
> appreciated.

When I introduced locations as tzdb identifiers long ago, I naively put 
in one Zone or Link per country. Some users got accustomed to the idea 
that Zone and/or Link status was akin to political recognition of 
countries or their boundaries (is Kosovo a country? is Jerusalem part of 
Palestine? that sort of thing) and so I eventually realized my mistake: 
the identifiers are now supposed to be single locations, decoupled from 
countries or national regions.

At one point I attempted to simplify the database by coalescing regions 
that crossed country boundaries, since there's no longer any need to 
conflate the two. Unfortunately this flustered some users who thought 
this meant disrepect to particular countries (which was not the intent). 
After some back and forth we ended up with the current wording, which 
I'm not happy with, as the current rules are still too political and we 
still end up with "There should be an entry for Hanoi/Beijing/etc.!" 

If this continues to be a sore spot, I'm inclined to adjust the rules so 
that there need not at least one Link or Zone per country. This should 
help simplify future maintenance if, say, the US splits into multiple 
countries (and stuff like that does happen).

> I see there are recommendations for implementers regarding
> localization (e.g., reference to Unicode CLDR), but I could not find
> recommendations concerning the usage of tzdb names/ids/links/aliases -
> which, in my understanding, will be the String persisted by most
> applications in the end?

Although the "Names of timezones" section in 
<https://data.iana.org/time-zones/theory.html> talks about this, it 
sounds like you think something is missing. I'm not sure what sort of 
recommendations you're thinking about, though. Perhaps you could suggest 
a specific wording change to that section?

> setting "Vietnamese" data or systems to an "Asia/Bangkok" tzdb
> identifier would, to some degree, effectively tie that data to Thai
> legislation.

No, it ties that data to our best guess of what northern Vietnam etc. 
will do. It does not tie the data to any legislation, just as setting 
"Moroccan" data or systems to "Africa/Casablanca" ties that data to our 
best guess of what Morocco will do, regardless of existing legislation. 
In both cases our guesses may well be wrong and if so users will need to 
deal with the wrong guesses, which is just part of life when predicting 
the future. If we started letting political considerations affect how we 
record our guesses, that would lead to more controversy and more 
database churn and I'd rather not go that direction.

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