[tz] [PROPOSED] Support SAVE suffixes, for Namibia 1994-2017

Paul G paul at ganssle.io
Sun Apr 8 02:19:13 UTC 2018

I think there's a good chance Namibia is using the word "standard" in a different way than is meant by the distinction between "standard" and "daylight saving" times in this instance. They may mean "standard" in the sense of "the time used in Namibia is standardized to X."

While I don't disagree with the proposed expansion of the zi format to *allow* for this, for the specific case of Namibia, it would probably be a good idea to try and find evidence of whether the people of Namibia consider their "standard" time as shifting back and forth, or whether they consider one to be the "standard" offset.

On 04/07/2018 09:21 PM, Paul Eggert wrote:
> [Changing the Subject: line from [PROPOSED] Namibia was on DST until 2017-10-24"".]
> Michael H Deckers via tz wrote:
>>      See [www.lac.org.na/laws/1994/811.pdf].
>>      So both summer and winter time are called
>>      "standard" (which differs from the use in Ireland),
> Thanks, good catch. So: not only was the proposed patch incorrect for Namibia, tzdb has been wrong since tzdata1997i, since it said that Namibian summer time was daylight saving time, and this wasn't correct either.
> zic does not have a convenient notation for Namibia's timekeeping practices in 1994-2017, when standard time was changed twice per year in a regular pattern. Although tzdb can explicitly list each transition, that's awkward and error-prone; it's better to use Rule lines. Attached is a proposed patch to do that, by slightly extending the syntax of Rule lines so that an entry in their SAVE columns can have an 's' suffix if you want the corresponding rule to specify standard time. For completeness, the new 'd' suffix specifies daylight saving time.
> Since this is an extension to zic input format, it's a vanguard feature, which means that the patch causes the new feature to be used in vanguard.zi but not in the traditional 'africa' file. We will wait a while before migrating it into 'africa'. As usual, people can test their tzdata parsers on bleeding-edge-format data by running the parsers on 'vanguard.zi'.

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