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

[Guy Harris]

On Feb 19, 2019, at 8:34 AM, Paul Eggert <eggert at cs.ucla.edu> wrote:

> Hans-Joerg Happel wrote:
> 
>> 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.

...and if they do something that doesn't match our guess, so that it differs from what's done in Thailand, we'd probably end up pulling Asia/Hanoi out of the backzone file, put it into the asia file, and changing it as appropriate.

For example, if Vietnam were to introduce summer time when Thailand doesn't do so, or when Thailand does so with different rules, we'd probably:

	pull Asia/Hanoi out of backzone and put it into asia;

	add summer time rules for Vietnam;

	change both Asia/Hanoi and Asia/Ho_Chi_Minh to refer to those rules;

(and, in the latter case, add summer time rules as appropriate for Thailand and modify Asia/Bangkok to use them).

(Now *that's* the kind of government action that would get us to introduce Asia/Hanoi as a non-backzone tzdb region. :-))