[tz] Issues with pre-1970 information in TZDB

Paul Eggert eggert at cs.ucla.edu
Thu Sep 23 16:58:31 UTC 2021

On 9/22/21 12:34 PM, Tom Lane via tz wrote:

> 1. It's not possible to separate the new backzone zones from the old.

No, actually it is possible. I've done it, by using the patch I 
described here:


That patch does exactly the separation you describe. It separates the 
new backzone Zones from the old ones. When using it, I obtained 
tzdata.zi and TZif files that exactly matched 2021a except for the 
changes you're not objecting to. I verified the match by zdumping the 
resulting TZif files and comparing the outputs. This all took quite a 
bit of work, but it was work I was willing to undertake to avoid the (to 
mind worse) alternative of forking tzdb.

> 2. This approach puts it on individual tzdb distributors to decide
> which of these two options to choose.

Yes, that problem is inherent to any fork or option-equivalent-to-fork. 
That's one reason I recommended against using the patch. Another reason 
- more important to my mind - is that sticking with 2021a's blueprint 
would mean that its equity problems would remain present in whoever uses 
that blueprint.

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