[tz] Dropping coordinates from zone1970.tab?

Guy Harris gharris at sonic.net
Thu Sep 30 09:25:52 UTC 2021

On Sep 30, 2021, at 1:57 AM, Aurelien Jarno <aurelien at aurel32.net> wrote:

> On 2021-09-30 01:28, Guy Harris wrote:
>> On Sep 30, 2021, at 12:51 AM, Aurelien Jarno via tz <tz at iana.org> wrote:
>>> The point is not about choosing a timezone from a location, but rather
>>> being able to show the cities linked to the timezones on a map so that
>>> end users can pickup their timezone visually.
>> "Cities linked to the timezones" as in "the cities whose names appear in the tzids of the regions", or as in "cities located within the regions"?
>> The latter sounds far more useful to users than the former, as that way the end user can look for the city nearest to them, *even if that city doesn't happen to be the one used in the tzid for their region*.  It would also let them type in the name of a city near them to specify the region they're in (as long as the city isn't both near them *and* in a different zone.)
> I am talking about the "the cities whose names appear in the tzids of
> the regions", independently if they appear as tzid or as a link.

End users should neither have to know or care about tzids.

>>> While timezones concept
>>> might sometimes be difficult to end users, they are usually aware if a
>>> city near to their location "has the same time or not".
>> "Has the same time" as what?  Presumably not the city whose name appears in the tzid of the region, as users shouldn't have to be aware of tzids.
> I am putting myself in the end user perspective. They do not know a lot
> about timezones, however they usually know if the nearby cities from
> their country follow the same rules regarding the time as the place they
> live.

Anybody who puts themself in the end user perspective should start by saying "how can I let the user select a tzdb region without having to know anything about tzids?"  For a general-purpose computer with a GUI, both Apple and Ubuntu have done so; see the mail I sent before this one.

>>> Note that all the information for providing nice ways to select a
>>> timezone for end-users is available in zone.tab,
>> zone.tab has the boundaries of tzdb regions as well as the names of sufficiently significant cities in each region?  I don't see the names of the two largest cities near me in that file, much less the name of the smaller city in which I live, so I don't see any way to construct a nice way to select a timezone from that data.
> Again you do not need the boundaries. Do you see the country where you
> live in that file,

Yes, but I don't see the city in which I live.

> and at least one city? Unless you live in Bouvet
> Island or Heard Island and McDonald Islands, two uninhabited regions,
> that should be the case. This means that you can be presented with a map
> with cities to pick-up.

Yes, I can be presented with a map that I can use to indicate to the computer what tzdb region I want.

On my host machine, I can do so just by popping up System Preferences, selecting "Date & Time", clicking the padlock if it's locked and entering my password (as my account has administrator privileges), and un-checking "Set time zone automatically using current location".

On my Ubuntu 18.04 and 20.04 guest machines, I can do so by just clicking "Activities", entering "time zone", selecting "Date & Time", turning off "Automatic time zone" if it's on (which it isn't, on those machines), and click "Time Zone".

> Yes you need some clue to pick-up the right one,
> but far less than when you have to pick-up Toronto when living in
> Bahamas.

If you're showing a map with cities, it should show Nassau, because that's a significant city; you shouldn't restrict yourself to cities with names that happen to appear in the name of a tzdb Zone.

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