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

Stephen Colebourne scolebourne at joda.org
Sun Apr 8 09:55:19 UTC 2018

I agree with Paul G. The meaning of "standard" here is "standardized"
or "common across the country".

"Iivula-Ithana told the NA that Cabinet decided that Namibia should
have summer time as standard time."
implying that use of "summer time" trumps reference to "standard time.
"The country changes to winter time in April, but the Zambezi region
maintains summer time all year."

"NAMIBIA enters its five-month-long winter time period at 02h00 on
Sunday when the official time will be changed an hour back, to 01h00.
Official summer time returns at 02h00 on the first Sunday in
September [September 5 this year], when the country's standard time
shifts an hour forward again."

" the new law seeks to repeal the Namibian Time Act of 1994 to set the
standard time to two hours in advance of Greenwich Mean Time"
Note it is "the standard time" not "standard time".

Video, no mention of "standard time"

Video, refers to winter, summer and "national time", not "standard time"

Together with other links, it clearly suggests that "winter time" and
"summer time" are in common parlance. That the word "standard" is also
used simply doesn't have the meaning TZDB uses for that word.

The TZDB is_dst flag should express that there is a relationship
between the times within the year, ie. one is for summer (and therefor
the other is implicitly winter). Given this, there is no need to
introduce a change to the source format.

I do agree that the evidence is that Namibia viewed switching to
winter time as DST (a negative SAVE), although I continue to think
that is irrelevant to the purpose and goals of TZDB.

The old law is here:

The new law is here:

And just for fun, here are some references about the area around
Zambezi in eastern Namibia. Maybe this is enough historical evidence
for that region to have its own ID?


On 8 April 2018 at 03:25, Paul G <paul at ganssle.io> wrote:
> The Wikipedia article (https://en.wikipedia.org/wiki/Time_in_Namibia) leads me to this story suggesting that Namibians consider themselves as switching to "Winter Time" (as is the case in Ireland): https://www.newera.com.na/2016/03/24/grn-evaluates-winter-time-change/
> This one similarly suggests that they think of themselves as switching to "Winter time": https://www.namibian.com.na/161621/archive-read/Time-change-divides-lawmakers
> Regardless of how the law is worded, I think people considered summer to be the standard time rather than always being on 'standard time' and the offset switching twice per year.
> On 04/07/2018 10:19 PM, Paul G wrote:
>> 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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