Info on timechanges in Sweden

Paul Eggert eggert at
Fri Apr 20 05:20:02 UTC 2001

Thanks very much for your analysis of the history of local time in
Sweden.  Here are some comments I have in response.

> From: Ivan Nilsson [mailto:ivan at]
> Sent: Friday, April 13, 2001 6:46 PM
> I suggest SEST rather than SST or ST because other time standards
> already use them (SE = the internation code for Sweden).

In similar situations, we've been using "xxT" to represent "xx Time"
(where xx is the country code), so "SET" would be the logical
abbreviation.  This is an after-the-fact abbreviation, as two-letter
country codes are a relatively recent invention, and if we ever find
out what English-language abbreviation (if any) was used back then, we
should replace "SET" with that abbreviation.

> "September 30 1916 is considered to end one hour later".
> This is a most ambiguous statement.

It is unclear, but I take it to mean that 1916-09-30 had 25 hours
rather than the usual 24, and the most natural way to model this in
the tz database would be to move the clock backwards by one hour at
24:00 that day.  It would make less sense to move the clock backwards
at 01:00 the next day (unless perhaps the legal day in Sweden back
then was not from 00:00 to 24:00 as it is now?).

> the time 1:00:00 is in no way involved in the summertime changes in
> Sweden nowadays.

I think the tz database is OK on this point, as it specifies a
transition time of 01:00 UTC for both transition times, as required by
the EU.  This is equivalent to the CET and CEST transition times that
you mentioned.

Thanks to your message, here is the revised Zone that I'll suggest in
my next proposed patch.  If you see any further trouble with it,
please let me know.

Zone Europe/Stockholm	1:12:12 -	LMT	1879 Jan  1
			1:00:14	-	SET	1900 Jan  1	# Swedish Time
			1:00	-	CET	1916 May 14 23:00s
			1:00	1:00	CEST	1916 Sep 30 23:00s
			1:00	-	CET	1980
			1:00	EU	CE%sT

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