[tz] Adding verified historic details

Lester Caine lester at lsces.co.uk
Wed Sep 4 15:46:10 UTC 2013


I sat down and worked my way through the UK details to see what is documented 
and what not. I'm normally using the results rather than the raw data, but I 
think I understand how this works now. I'm still using my own code in parallel 
with the version of TZ that Derick has built into the PHP clock tools so the 
main thing here is now comparing results. I've even got the original emails 
still archived.

I've been using the 1880 'legal' date for the adoption of GMT and calling 'the 
other time' Railway time, but I can accept combining them. However the documents 
are all legal ones so using 'legal' time so midnight for a change was legal 
midnight not GMT until 1880 - that's politics for you :)

As far as I am concerned, the Isle of Man was using LMT until 1883 and we now 
have a date of 30th March to go with that. I've always worked with 18 minutes 
offset, although Tynwald which is always quoted as the reference is 4.4814degW - 
17m55.5s and that goes back 1000 years, but I think we can skip earlier solar times.

So looking at the Europe data file ...

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
			 0:00	GB-Eire	%s	1996
			 0:00	EU	GMT/BST
Link	Europe/London	Europe/Jersey
Link	Europe/London	Europe/Guernsey
Link	Europe/London	Europe/Isle_of_Man

I think I need to add ...

# AT4 of 1883 - The Statutory Time et cetera Act 1883 -
Zone	Europe/Isle_of_Man 0:17:55 -    LMT 1883 March 30 0:00s

Then the London Rules apply from then so in my simple way of thinking

Link	To	Europe/London ( date is optional as on line above? )

Fills the picture. Europe/Isle_of_Man exists in it's own right up to 1883, and 
then it follows Europe/London.

I'm fairly sure from the IOM documents that Jersey and Guernsey followed the 
same date, but their archives have not got that far back yet. So do we have to 
duplicate the whole zone record each timezone to add this one item of data?

- -
Lester Caine - G8HFL
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