In 1916 time and times in Ireland changed forever.
When the G.P.O. clock stopped at 2.25 p.m. during the Easter Rising of 1916 it was operating under Dublin Mean Time. ‘London Time’ was 2.50 p.m. (G.M.T.) at that moment.
The Statutes (Definition of Time) Act of 1880 defined Dublin Mean Time as the legal time for Ireland. This was the local mean time as measured at Dunsink Observatory, where sunrise and sunset were 25 minutes and 21 seconds later than at Greenich Observatory in London. James Joyce mentions ‘Dunsink time’ five times in his novel Ulysses. Later in the year the Time (Ireland) Act 1916 defined the legal time for Ireland to be Greenich Mean Time and time changed in Ireland at 2:00 am Dublin Mean Time on 1st October 1916. When British clocks went back an hour for winter on Sunday, 1st October 1916, Irish clocks went back by only 35 minutes to synchronise clocks in Ireland and Britain.
There was some opposition from local councils, politicians, farmers and some business groups. Countess Markievicz complained bitterly about the change, writing that “public feeling was outraged”.