[tz] tzdb timezone names/identifiers and links

Fred Gleason fredg at paravelsystems.com
Tue Feb 26 19:49:38 UTC 2019

On Tue, 2019-02-26 at 11:06 -0800, Guy Harris wrote:
> Have you ever had one of them say "I'm in Beijing, but you're only
> offering me Shanghai"?

Not yet, though I imagine it's just a matter of time. :)

> Nothing obliges you to use the tzdb identifiers rather than, say,
> names that might not require knowing how tzdb region IDs are chosen,
> e.g. "China" as the name for Asia/Shanghai (and something else, such
> as Xinjiang or Urumqi, for Xinjiang time),

That is, unless you are an ethnic Han living in the Western Regions, in
which case you probably want Asia/Shanghai after all. 'Automatic
location detection' does not address that case well either.

My basic take is this: civil timekeeping is quite complex enough as it
is, without the arbitrary interposition of yet more layers of
indirection in the zone indexing. In many (perhaps most?) applications,
such indirection may be a necessary evil. However, anything that
increases the overall global complexity of a system imposes a 'tax' of
its own (both in system resources and in the ease with which the system
can be modeled and understood in a programmers head). It's well to
consider this cost in the overall context of the intended use case,
platform capabilities and intended user audience. To issue a
categorical imperative like 'tzdb identifiers should *never* be shown
to users' is to short-circuit this entire delicate design process of
weighing tradeoffs.


| Frederick F. Gleason, Jr. |             Chief Developer             |
|                           |             Paravel Systems             |
| But in our enthusiasm, we could not resist a radical overhaul of    |
| the system, in which all of its major weaknesses have been exposed, |
| analyzed, and replaced with new weaknesses.                         |
|                                                                     |
|                     -- Bruce Leverett                               |
|                     "Register Allocation in Optimizing Compilers"   |

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