[tz] Europe/London Sat Oct 26 23:00:00 1968 UT

Brian Inglis Brian.Inglis at systematicsw.ab.ca
Mon Sep 15 05:25:01 UTC 2014


On 2014-09-14 22:40,  "" wrote:
> Looks like isdst should be 1 on
>      Europe/London  Sat Oct 26 23:00:00 1968
> and
>      Europe/London  Sun Oct 31 01:59:59 1971
> zdump -v -c 1968,1973 Europe/London
> Europe/London  -9223372036854775808 = NULL
> Europe/London  -9223372036854689408 = NULL
> Europe/London  Sun Feb 18 01:59:59 1968 UT = Sun Feb 18 01:59:59 1968 GMT isdst=0 gmtoff=0
> Europe/London  Sun Feb 18 02:00:00 1968 UT = Sun Feb 18 03:00:00 1968 BST isdst=1 gmtoff=3600
> Europe/London  Sat Oct 26 22:59:59 1968 UT = Sat Oct 26 23:59:59 1968 BST isdst=1 gmtoff=3600
> Europe/London  Sat Oct 26 23:00:00 1968 UT = Sun Oct 27 00:00:00 1968 BST isdst=0 gmtoff=3600
> Europe/London  Sun Oct 31 01:59:59 1971 UT = Sun Oct 31 02:59:59 1971 BST isdst=0 gmtoff=3600
> Europe/London  Sun Oct 31 02:00:00 1971 UT = Sun Oct 31 02:00:00 1971 GMT isdst=0 gmtoff=0
> Europe/London  Sun Mar 19 01:59:59 1972 UT = Sun Mar 19 01:59:59 1972 GMT isdst=0 gmtoff=0
> Europe/London  Sun Mar 19 02:00:00 1972 UT = Sun Mar 19 03:00:00 1972 BST isdst=1 gmtoff=3600
> Europe/London  Sun Oct 29 01:59:59 1972 UT = Sun Oct 29 02:59:59 1972 BST isdst=1 gmtoff=3600
> Europe/London  Sun Oct 29 02:00:00 1972 UT = Sun Oct 29 02:00:00 1972 GMT isdst=0 gmtoff=0
> Europe/London  9223372036854689407 = NULL
> Europe/London  9223372036854775807 = NULL

The relevant rules, comments, and zones to examine in data/europe are:

# Summer Time Order, 1968 (S.I. 1968/117)
Rule	GB-Eire	1968	only	-	Feb	18	2:00s	1:00	BST
# The British Standard Time Act, 1968
#	(no summer time)
# The Summer Time Act, 1972
Rule	GB-Eire	1972	1980	-	Mar	Sun>=16	2:00s	1:00	BST
Rule	GB-Eire	1972	1980	-	Oct	Sun>=23	2:00s	0	GMT

and:

# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
Zone	Europe/London	-0:01:15 -	LMT	1847 Dec  1  0:00s
			 0:00	GB-Eire	%s	1968 Oct 27
			 1:00	-	BST	1971 Oct 31  2:00u

which gives 1968 Oct 27 midnight as the transition from British Summer Time
isdst=1 to British Standard Time isdst=0 both with GMT offset +1.00, from
the British Standard Time Act 1968 c. 45, whichended itself effective
1971 Oct 31 2.00 GMT.

See http://polyomino.org.uk/british-time and search for "1968 c. 45".
-- 
Take care. Thanks, Brian Inglis


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