[tz] [PROPOSED] Merge timezones that are alike since 1970

Guy Harris gharris at sonic.net
Wed Jun 2 02:42:36 UTC 2021

On Jun 1, 2021, at 5:57 PM, David Patte via tz <tz at iana.org> wrote:

> I write both astronomy and family history apps, and I write my own parsers to extract the data I  want from tz tables on the fly. I believe many using the historical data portion of tz would likely do the same thing. Type (2) people simply want to continuously improve the accessibility, locality and accuracy of historical tz data, for apps that want PAST tzdata, not future tz data.

It's not a difference between wanting past data vs. wanting future data.

OSes definitely use past tz data:

	$ ls -lT /usr/local/bin/yacc
	-rwxr-xr-x 1 root wheel 123916 May 6 14:18:05 2018 /usr/local/bin/yacc

The difference is how far back in time is useful, not whether the past is useful at all.

For OS purposes, times before the OS's time stamp epoch are probably of less interest than times at or after the epoch, and for many OSes, even times after the epoch but before the first release of the first OS to use any file system supported by the OS are of less interest.

The UNIX epoch is probably a good dividing line between the two groups.

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