[tz] Issues with pre-1970 information in TZDB

Tom Lane tgl at sss.pgh.pa.us
Wed Sep 22 23:02:10 UTC 2021

I wrote:
> 2. This approach puts it on individual tzdb distributors to decide
> which of these two options to choose.  Some will choose differently
> than others, meaning we'll now have two received versions of tzdb,
> which is as bad as a fork from the perspective of end users.

> (It was argued that we already have problem #2 because some distributors
> already use backzone.  AFAICT that's only a small minority though.
> It'd likely become a much bigger issue.)

To put some detail on that claim ... I ran around and checked systems
I had handy to see whether the vendor-provided tzdb includes backzone.
I checked this by seeing whether Africa/Timbuktu contained different
data from Africa/Abidjan, which hasn't been true since 2014f unless
you built with backzone.  (Some of the system images I checked are a
year or two old, but it seems unlikely that any vendors would have
changed their policies recently.)  Of

	Red Hat (both Fedora and RHEL)

not one is building with backzone.  I think it's reasonably safe to
assert that the current population of backzone users is negligible.

(Of course, Windows would be the elephant in the room here, but last
I heard Windows uses their own timezone database not tzdb.)

			regards, tom lane

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