[tz] Preparing to fork tzdb

Clive D.W. Feather clive at davros.org
Sat Sep 25 22:21:50 UTC 2021

Robert Elz said:
>   | I see that point, though it depends on how you view pre-1970 data. After
>   | all, the data is already wrong for much of the area covered by
>   | Europe/Berlin and possibly (I wouldn't be surprised either way) much of
>   | the area covered by Europe/Oslo.
> It isn't "because they're different countries" but because there was
> data that is now (effectively) deleted

So, at the risk of putting words into your mouth that weren't there, you
want to bring everything from backzone into the main distribution and have
a policy of not getting rid of any zone that already exists? That's an
arguable position (I don't know at this point if I agree with it) that's
worth talking about.

> In other words, any authority with the ability to make timezone changes
> who wants to have their own zone, with their own data (including as much
> of their own historical data as they can manage to collect) simply needs
> to change their timezone in some small way, and we have no choice but to
> give them a zone, after which they can submit the historical (pre 1970)
> data, and it will be included.

That's always been the case. I've not seen any authority bothering to do
that, though - given that they don't bother to tell us about changes until
a few days before, we clearly aren't high up on their list of important
things to worry about. So I don't think this is a significant risk.

> To the extent that we're concerned that even though Berlin is the
> correct choice for Germany according to the rules, its time history
> is not accurate for much of the rest of Germany, then there's nothing
> stopping us treating this as a somewhat special case (which it clearly is),

>From another email, it's not just Berlin that's a special case. Just about
every zone in the USA is a similar special case because, to paraphrase,
until the mid-1960s practically every village had its own date for DST

> That the data doesn't differ post 1970 does not exclude a new zone, it
> just does not require that one be created, there's a discretion.

I can accept that.

Clive D.W. Feather          | If you lie to the compiler,
Email: clive at davros.org     | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
Mobile: +44 7973 377646

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