[tz] Irish time...
Joseph S. Myers
jsm at polyomino.org.uk
Sun Oct 16 13:43:57 UTC 2011
On Sun, 16 Oct 2011, Kevin Lyda wrote:
> The first entry in the europe zone file for Ireland is as follows:
>
> Rule GB-Eire 1916 only - May 21 2:00s 1:00 BST
> However I don't think it's correct. I'm not sure how far back we want
> to go, but apparently from 1880 up until October, 1916, Dublin was 25
> minutes off from London. When the clocks were set back in October
> 1916, they were set back 35 minutes - which would seem to cast doubt
> on the second line for GB-Eire:
>
> Rule GB-Eire 1916 only - Oct 1 2:00s 0 GMT
The effect as shown by zdump appears to be correct:
Europe/Dublin Sun May 21 02:25:20 1916 UTC = Sun May 21 01:59:59 1916 DMT isdst=0 gmtoff=-1521
Europe/Dublin Sun May 21 02:25:21 1916 UTC = Sun May 21 03:00:00 1916 IST isdst=1 gmtoff=2079
Europe/Dublin Sun Oct 1 02:25:20 1916 UTC = Sun Oct 1 02:59:59 1916 IST isdst=1 gmtoff=2079
Europe/Dublin Sun Oct 1 02:25:21 1916 UTC = Sun Oct 1 02:25:21 1916 GMT isdst=0 gmtoff=0
That is, the clocks went forward one hour at 2am DMT on 21 May, and then
at 2am DMT (3am summer time) on 1 October they went to GMT. See attached
scans of the relevant laws.
The relevant UK National Archives file has a public information poster
used in Ireland to inform people of the 35-minute clock adjustment. What
times people were actually using in Ireland, I don't know.
I have not attempted a thorough survey of Irish laws relating to time; my
2005-01-26 comment in the europe file lists those I found (though those
URLs seem to have become broken since then) but I haven't attempted to
match them up to individual transitions and add comments for each
transition giving the Irish legal basis for it alongside those giving the
British basis.
--
Joseph S. Myers
jsm at polyomino.org.uk
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