[Datetime-SIG] Computing .dst() as a timedelta

[M.-A. Lemburg]

On 21.09.2015 17:01, Alexander Belopolsky wrote:
> On Mon, Sep 21, 2015 at 8:44 AM, M.-A. Lemburg <mal at egenix.com> wrote:
> 
>> Interesting. It lists two "DST"s per year: they first
>> go from GMT to CET, then to CEST, and then back to CET and GMT.
>> I guess they switched to CET when the station was used and
>> to GMT for the instruments during winter when it was not used.
>>
>> But this is not consistent with what the Norwegians report on their
>> Troll station website:
>>
>> http://www.npolar.no/en/about-us/stations-vessels/troll/index.html
>>
>> """
>> The time zone Troll is located in, UTC +0, is 1 hour behind Norwegian
>> time (2 hours during summer time in Norway). Photo: Norwegian Polar
>> Institute
>> """
>>
>> The webcam confirms this:
>> ftp://ftp.npolar.no/Out/TrollWebCam/TrollPublic.jpg
>>
> 
> For those who care about this kind of timezone trivia, apparently [1] Troll
> station is inhabited by Norwegians only during the colder months
> (March–October)
> who use Norwegian time (TZ=Europe/Oslo).  During the warmer ("busy")
> season, the station switches to UTC as an option that is equally annoying
> to all international inhabitants.
> 
> The specific rules that appear in some versions of the IANA zone info files
> are pure fantasy.
> 
> [1]: http://mm.icann.org/pipermail/tz/2014-March/020705.html

Looks like assigning a "time zone" to the place is simply conceptually
wrong and was just done to make some tz folks happy.

Anyway, the main takeaway for me is that it is obviously possible
to have more than two DST switches during the year, which is
something I wasn't aware of before seeing this example.

-- 
Marc-Andre Lemburg
eGenix.com

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