[tz] tzdb timezone names/identifiers and links

Guy Harris guy at alum.mit.edu
Fri Mar 1 11:05:28 UTC 2019

On Mar 1, 2019, at 2:41 AM, Martin Burnicki <martin.burnicki at meinberg.de> wrote:

> With "location name" I just meant mean what is displayed to the ordinary
> user, which eventually is even localized.
> For users in Germany Düsseldorf, Hamburg, Munich or Berlin is fine, but
> Stockholm probably not since users are not sure if Stockholm has the
> same TZ rules as Germany.

Well, that pretty much shows that tzdb IDs are not the right answer, given that users might not know that, for example, Hanoi has (since 1970) the same offset and summer time rules as Bangkok.  It even says that mapping from a tzdb ID to something "more friendly" won't work in those cases.

So, if a user really wants to know what time zone rules are being invoked at the current location, we need a way to describe them that wouldn't be meaningless noise to a user, e.g.

	{name} summer time rules

with {name} being the name of an appropriate region - probably including the country you're currently in, but that isn't sufficient in many cases - and "summer time rules" appropriately localized, e.g. "Daylight Saving Time rules" in the US.

{name}, as indicated above, is not something that can be looked up in a table given only a tzdb ID; you'd also need some indication of your physical location, so you'd get

	German summer time rules

in Berlin, Düsseldorf, Hamburg, Munich, etc. and

	Swedish summer time rules

in Stockholm, Gothenburg, Uppsala, etc., and so on.

Or you could just dump out the rules - but one of the good things about the tzdb is that it reduces the chances that you need to *know* the rules, so dumping out the rules might be telling the user something they don't know and don't even want to know.

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