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@polyomino.org.uk