[tz] Moving more zones to 'backzone'

Paul Eggert eggert at cs.ucla.edu
Fri Aug 12 09:10:19 UTC 2022

On 8/11/22 05:39, Peter Krefting wrote:

> The zone1970.tab files provides me with a list of time zones, one per 
> country

Not sure about the "one per country" part. Some countries have more than 
one Zone, and some Zones have more than one country.

> With the zone1970.tab change in 2022b, it is not immediately obvious 
> that for Norway, I should select "Berlin" (although I have added the 
> commentary, so it does say "Scandinavia").

Column 1 of the zone1970.tab entry for Europe/Berlin lists NO (Norway) 
as one of its country code, so if software looks at column 1 it should 
easily deduce that Europe/Berlin covers at least part of Norway.

This sort of issue is not new to 2022b. For example, if software ignores 
zone1970.tab's column 1 it's not immediately obvious that Europe/Prague 
covers at least part of Slovakia, and this has been true ever since 
zone1970.tab was introduced in release 2014f.

> I will have to experiment with changing the code to parse the 
> zone1970.tab country list, and break it up by that, showing only the 
> country name and the comment in the selector.

Yes, something like that needs to be done regardless of whether 2022a or 
2022b is being used.

In looking into this I did notice, though, that tzselect will be 
confused by 2022b's changes for Iceland, in that 2022b's tzselect 
doesn't know that Iceland is in the Atlantic, which means if you first 
select Atlantic, the secondary menu won't mention Iceland. Again, 
though, this sort of issue is not new to 2022b. For example, in 2022a 
tzselect if you first choose the Atlantic, tzselect doesn't know that St 
Helena is in the Atlantic and so its secondary menu won't mention St 
Helena. Here's another example: if you first choose Asia, 2022a tzselect 
doesn't know that Turkey is in both Europe and Asia and so its secondary 
menu doesn't mention Turkey.

To work around this longstanding problem I installed the attached 
proposed patch, which adds comments to zone1970.tab to help tzselect 
avoid the problems mentioned above, and similarly for Cyprus, Svalbard, 
Mayotte, etc. I view these comments as experimental; if they work well 
we can promote them to full-fledged data in some future release and if 
not then perhaps we can think of something better.
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