[tz] Issues with pre-1970 information in TZDB

Tom Lane tgl at sss.pgh.pa.us
Thu Sep 23 17:31:38 UTC 2021

Paul Eggert <eggert at cs.ucla.edu> writes:
> On 9/23/21 7:32 AM, Tom Lane via tz wrote:
>> That's half of the issue.  The other half is "if a zone does not contain
>> relevant pre-1970 data, how would end users know that?"

> For most users the answer is simple: the pre-1970 data should not be 
> relied upon for anything other than an estimate. That data are intended 
> only for exact locations named, and most people in the world do not live 
> in those exact locations.

That's fine, but if that is the policy, then the data should in fact be
valid (to the best of our ability) for the named location.  It's not okay
to present data for Europe/Oslo that is simply known incorrect for Oslo.
Whether it's exact for anywhere else in Norway is a red herring.

In other words, I'm of the opinion that the answer to my question above
should be "we don't ever do that".  Right now, it isn't.

			regards, tom lane

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