[tz] Issues with pre-1970 information in TZDB

Tom Lane tgl at sss.pgh.pa.us
Wed Sep 22 21:17:50 UTC 2021

Guy Harris via tz <tz at iana.org> writes:
> Presumably "stability" here includes "don't convert existing tzdb regions to links merely because they have the same 1970-and-later data" (putting them into the "don't merge" camp); does it also include "don't split existing tzdb regions due to the discovery that different parts of those regions had different pre-1970 data"?  (Those who want a full historical record of time zone data would presumably want those existing regions split.)

For my own purposes, splits are not particularly problematic as long as
the existing name can keep the existing historical data --- nobody is
forced to adopt the new zone immediately, and whatever stored timestamps
they have still mean the same thing.

It gets a little more exciting if we discover that, say, Europe/Berlin's
back data is more appropriate to some other place than it is to Berlin.
OTOH, it's not clear how that differs from "Europe/Berlin's back data
is wrong", so probably we'd just fix it and move on.

In general, I think that incremental changes that clearly (or at least
plausibly) improve the accuracy of tzdb's description of reality are
fine.  One thing that's particularly sticking in my craw about the
changes under debate is that they undeniably made tzdb worse as a
description of reality in the places at issue.

			regards, tom lane

More information about the tz mailing list