[tz] Adding verified historic details

Lester Caine lester at lsces.co.uk
Thu Sep 5 10:28:45 UTC 2013

Joseph S. Myers wrote:
> On Wed, 4 Sep 2013, Lester Caine wrote:
>> Fills the picture. Europe/Isle_of_Man exists in it's own right up to 1883, and
>> then it follows Europe/London.
> Well - subject to confirming it did so during WW2, as you drew my
> attention to that issue.  The (UK) Emergency Powers (Defence) Act, 1939
> includes provision (subsection 4(1)(a)) for it to be extended to the Isle
> of Man by Order in Council, but I don't have a specific reference to such
> an Order in Council (presumably a UK SR&O) doing so.  (All the subsequent
> regulations then worked by modification of an Act also applying to the
> Isle of Man, so if they had the power to apply there then they would have
> done so.)
>> 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?
> We have dates of legal adoption of GMT in Jersey (around 4pm on Saturday
> 11 June 1898) and Guernsey (18 June 1913).  What we don't have is full
> details from WW1 or WW2, beyond the quote about time being put forward
> under occupation in WW2
> (https://en.wikipedia.org/wiki/File:Orders_of_the_German_Commandant_Evening_Post_2_July_1940.jpg
> gives one transition time as 11pm on 2 July 1940 in Jersey and we do have
> reasonably detailed information on German time from the PTB).  Certainly
> if the cut-off is 1945 or before, you need different data for them than
> for Europe/London and we don't have the full information (whereas after
> 1945, the links to Europe/London are probably correct).

A first pass at adding this data is logged on my repo - http://lsces.org.uk/hg/tz/
I'm not sure that I have included the war time period correctly? This is the 
part I'm still getting my head around.
Also the way locations used for calculating LMT are added may need to change?

In my mind an additional table ( I'm normally working all this in databases ) 
would provide a list of locations and dates when the transition was made to a 
standard time, along with a link to the appropriate rule set. A time zone is 
simply a list of the appropriate rule sets + the locations linked to them.

Lester Caine - G8HFL
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