Time in the Republic of Ireland

Ireland uses Irish Standard Time (IST, UTC+01:00; Irish: Am Caighdeánach Éireannach) in the summer months and Greenwich Mean Time (UTC+00:00; Irish: Meán-Am Greenwich) in the winter period. (Roughly two-thirds of the state is in the 7.5°W to 22.5°W sector, the other third is in the same sector as Greenwich: 7.5°E to 7.5°W.)

Although most of Ireland is located west of the 7.5°W meridian, thus belonging to -1 time zone, the Standard Time Act 1968 legally established that "the time for general purposes in the State (to be known as standard time) shall be one hour in advance of Greenwich mean time throughout the year". This act was amended by the Standard Time (Amendment) Act 1971, which legally established Greenwich Mean Time as a winter time period. Ireland therefore operates one hour behind standard time during the winter period, and reverts to standard time in the summer months. This is defined in contrast to the other states in the European Union, which operate one hour ahead of standard time during the summer period, but produces the same end result.

The instant of transition to and from daylight saving time is synchronised across Europe. In Ireland, winter time begins at 02:00 IST on the last Sunday in October (changing the clocks to 01:00 GMT), and ends at 01:00 GMT on the last Sunday in March (changing to 02:00 IST).

The following table lists recent past and near-future starting and ending dates of Irish Standard Time or Irish Summer Time (use of DST beyond 2019 is under discussion, see below):