[tz] Moving more zones to 'backzone'

[Florian Weimer]

* Clive D. W. Feather:

> Florian Weimer via tz said:
>> I'm not sure if the above is an appropriate characterization, but I want
>> to point out that switching much of Europe to Europe/Berlin will leaves
>> us ill-equipped to deal with future time zone fragmentation after
>> mandatory DST has been abolished in Europe, and different countries make
>> different choices.
>
> I disagree. In fact, I think it's scaremongering.
>
> Ignoring Ireland, which is already a special case, and overseas territories,
> which aren't affected anyway, there's only three current timezones in the EU
> (in terms of current rules, ignoring all history ever). If, for example
> Sweden decides to stay on winter time and the rest of the EU decide to stay
> on +2, then we split Europe/Stockholm back off Europe/Berlin *and do nothing
> else*. This is exactly the same as if we suddenly discovered that Sweden had
> changed time a week later than everyone else in 1984. And is no more work
> than if we'd discovered that Berwick-on-Tweed hadn't observed BST in 1976.

The benefit of the current scheme is that users can keep using
Europe/Stockholm (or the local equivalent for most European countries)
before and after the migration off DST.  This means they will be able to
implement the migration without a configuration change, just with a
software update.

If we tell them to switch to Europe/Berlin first, and then to some other
city outside their country, that creates unnecessary work and friction.

Thanks,
Florian