[tz] Issues with pre-1970 information in TZDB

[Michael H Deckers]

    On 2021-09-23 14:32, Tom Lane via tz asked:
> 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?"



    One way is to determine the offset local - UT for the distant past.
    Most tzdb timezones that are not links use an offset corresponding
    closely to the eastern longitude of the location, eg as given in
    zone.tab. (Locations assumed to be uninhabited in the far past are
    the exception.)

    Michael Deckers.