[tz] Issues with pre-1970 information in TZDB

Brooks Harris brooks at edlmax.com
Fri Sep 24 13:42:46 UTC 2021

On 2021-09-23 8:35 PM, Paul Eggert wrote:
> On 9/23/21 11:28, Brooks Harris wrote:
>> It seems these time zones could not be changed or merged to backzone. 
>> So what constitutes "pre-1970" and justifies a move to backzone?
> This is documented in the guidelines for timezone identifiers:
> https://data.iana.org/time-zones/theory.html#naming
> Look for "1970" on that page.
>  I gather
>> this 'merge' procedure began in 2015? Is there documentation or 
>> discussion of that decision?
> I think it was more like 2013 but do not recall the details. 
> Discussions are archived here:
> http://mm.icann.org/pipermail/tz/
Sure enough, a long discussion begins in 2013.

[tz] Dealing with Pre-1970 Data

There are no doubt many others in later years but its difficult to find 
in the archives. Further references appreciated.

Of course I've read 'theory' many times, and reviewed it again. But I 
still not understanding the criteria by which any time zone would be 
moved to 'backzone'. Let me try a simple example question:

Why is Asia/Tokyo retained while Europe/Oslo is moved?

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