[tz] Issues with pre-1970 information in TZDB

Tom Lane tgl at sss.pgh.pa.us
Thu Sep 23 22:20:23 UTC 2021

Guy Harris <gharris at sonic.net> writes:
> OK, then let's make that explicit in, for example, Theory, by indicating that if you use the pre-1970 data for a given tzdb region for anything other than the city that appears in the tzid, there is even less guarantee of correctness than if you use it for the city.

Seems reasonable.

> What if that data 1) has been determined to be correct based on sources we deem sufficiently reliable and 2) it applies to more than just the city and its environs, but it doesn't apply to, for example, the entire country?  Should one or more new tzdb regions be created for those other locations?

I think existing policy is that we don't make separate zones simply
because of pre-1970 differences.  I'm fine with continuing that, as
long as it's modulated by additional policies:

* I don't want to remove any existing zone, even if it's a zone that
wouldn't be created per current policy: the amount of grief we'd get
for that is just not worth it.

* And I do want to see some policy that allows new per-country zones to
be created, even if they don't currently differ from their neighbors.
I think that that would largely reduce political pressure from people
who feel that "XYZ ought to have its own zone", and it has the merit
of future-proofing tzdb against possible country-specific timekeeping
law changes.  For example, if Norway someday changes its laws such that
it's no longer identical to Europe/Berlin, then it's a whole lot less
painful all around if Europe/Oslo already exists and is already being used
by most of the affected users.  They'll just automatically get the right
time from a tzdb update, without having to adjust their settings.

As I've said before, I don't think the TZ Coordinator need be proactive
about creating such zones.  He need only be willing to accept suitably-
researched patches from people who are excited about those cases.

			regards, tom lane

More information about the tz mailing list