[tz] Time zone selection

Paul Eggert eggert at cs.ucla.edu
Mon Apr 18 16:52:29 UTC 2016

On 04/18/2016 09:04 AM, Matt Johnson wrote:
> To my knowledge, there is no project that maintains localized 
> translations for comments in zone.tab. Not even CLDR.

I don't know of any either. Perhaps CLDR could take this on too?

> I've computed a "threshold date" for each zone, where the zones are 
> identical from the threshold date forward. That date can be set by the 
> developer of the application to limit the subset of zones to choose 
> from without imposing too much opinion. I'm curious if anyone else has 
> explored this space before, or used similar techniques?

I did something along those lines, but gave up on it as being too hard 
to automate well. For example, if the threshold is 2001-01-01 00:00:00 
UTC, then we should merge America/Boise, America/Denver, 
America/Edmonton, and America/Yellowknife. How does the automated 
procedure choose the ID of the merged region? It should be 
America/Denver, as that has the greatest population, but how is the 
population recorded and what happens as population changes? Furthermore, 
how does the automated procedure derive the comment for the merged 
region?  And how would CLDR translate this automatically-derived comment?

For this reason I'm somewhat inclined to add one more hand-maintained 
table, zone-now.tab, which is like zone-1970.tab except using a cutoff 
of "now" (a deliberatly moving target) instead of a cutoff of 1970. That 
should be good enough for applications that don't need historical time 
stamps, and will be easier to automate and CLDRize.

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