[tz] tzdb timezone names/identifiers and links

Guy Harris guy at alum.mit.edu
Tue Feb 26 22:03:33 UTC 2019

On Feb 26, 2019, at 1:32 PM, Fred Gleason <fredg at paravelsystems.com> wrote:

> On Tue, 2019-02-26 at 12:14 -0800, Guy Harris wrote:
>> Is an ethnic Han living there less likely to realize that "China" is
>> more appropriate than "Xinjiang" or "Urumqi" for them than they are
>> to realize that "Asia/Shanghai" is more appropriate than
>> "Asia/Urumqi"?  If so, why?
> I suspect that there would be a fair amount of experimentation in
> either case, until the user found the 'correct' setting --i.e. the one
> that made his clock match that of the people around him with which he
> interacts.

Or you just put an explanation in the documentation for the western areas of China for their benefit.

>> So presumably the tradeoff here is implementation complexity that the
>> programmer's brain has to deal with vs. UI complexity that the end
>> user's brain has to deal with, with the indirection taking away UI
>> complexity for the end user (i.e., having to understand about the
>> notion of tzdb regions and their IDs).
> Exactly correct, which is why the intended audience must be taken into
> account when considering these tradeoffs. If that audience is "Aunt
> Millie on her cellphone", then I quite agree that presenting raw tzdb
> IDs is not the optimum UI choice. OTOH, if that audience consists of
> (say) professional engineers who deal with these sorts of issues
> routinely, then yes, they want the tzdb IDs, not some interpreted
> version of what I think they 'really' meant.

Actually, that's not a question of "pushing complexity away from the programmers", it's a question of "users who don't need to know the details, and whose heads would probably explode if forced to deal with the details" vs. "users who need, for technical reasons, to deal with the details".

People who deal with those issues and therefore have to know about tzdb regions should be clueful enough to know that the tzdb IDs are chosen not as user-friendly names and, therefore, that "but I'm in City X, not City Y!" is a complaint that should and will receive little sympathy here, as the Theory file states the rules we use to select the city, and "that's not how we pronounce the city's name" is a complaint to be addressed by getting the English-speaking community to change the name they use for the city (cf. Bombay -> Mumbai).

So, for that subset of professional engineers who have to know about not just time zones and summer time in general, but about tzdb regions in particular, you can use tzdb IDs.

If there are are engineers who have to know about tzdb regions, but aren't yet familiar with the tzdb, the documentation for whatever product is being discussed should explain it to them - including the rules from the Theory file, so they understand that the names don't necessarily correspond to, and aren't intended to correspond to, the layman's notion of the name for a "time zone", or "the most important city in z time zone, for some definition of "most important"", or anything such as that.

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