[tz] Merged 1970+ time zones should always return -1 pre-1970

Paul Eggert eggert at cs.ucla.edu
Wed Sep 29 17:08:04 UTC 2021

On 9/29/21 9:32 AM, Robert Elz wrote:
>      Date:        Tue, 28 Sep 2021 16:38:30 -0700
>      From:        Paul Eggert via tz<tz at iana.org>
>      Message-ID:<086e075f-05fc-4f4f-a2ff-c4eeb2f2ab2f at cs.ucla.edu>
>    | Also, the 'backzone' line you're referring to ("-1:00 - -01 1960 Jun 20"
>    | [1]) is surely wrong,
> ... without evidence of the change happening at
> some other time, I would tend to believe that as it is written.   Independence
> had been agreed with France months earlier - that is, they had plenty of
> time to prepare, and was to happen (and happened) on that date.  Assuming
> that part of the preparation was to switch timezones along with independence,
> which is not an absurd suggestion

No, it is completely absurd. It's not how timezone rule changes work. No 
politician, no matter how amateur, would arrange to change the clocks 
merely because of Independence Day. It'd be a major political blunder if 
fiddling with the clocks is signaled as one of the most important things 
the new legislature or executive could do. And it would cause crowds to 
show up to parades at the wrong time.

That particular data entry must be wrong, and I can say this as someone 
with extensive experience reviewing dubious timezone data (unfortunately 
this is not a large club).

>   | The more we get bogged down with irrelevant 'backzone' trivia like the 
>   | date of Mali's independence,
> There's no need to get bogged down with that

Then let's not.

> why does Pacific/Honolulu still exist as a zone given the apparent
> policy?

It differs from all other Zones in its combination of UT offsets and 
timezone abbreviations.

My original proposal (now mostly reverted) involved writing a program 
that merged all Zones that agreed after 1970, so I doubt whether I 
missed any.

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