In Ireland, the Standard Time Act 1968 legally establishes 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 establishes Greenwich Mean Time as a winter time period. Ireland reverts to Irish Standard Time during the summer months. This is the reverse of the practice of other states in the European Union, but provides the same end results.
Before 1880, the legal time at any place in the United Kingdom of Great Britain and Ireland was defined as local mean time, as held by the appeal in the 1858 court case Curtis v. March. The Statutes (Definition of Time) Act, 1880 defined Dublin Mean Time as the legal time for Ireland. This was the local mean time at Dunsink Observatory outside Dublin, and was about 25 minutes 21 seconds behind Greenwich Mean Time (GMT), which was also defined by the Act to be the legal time for Great Britain. After the Easter Rising, the time difference between Ireland and Britain was found inconvenient for telegraphic communication and the Time (Ireland) Act, 1916 provided that Irish time would be the same as British time, from 2:00 am Dublin Mean Time on Sunday 1 October 1916.
After the Irish Free State became independent in 1922, subsequent developments tended to mirror those in the United Kingdom. This avoided having different times on either side of the border with Northern Ireland. Summer time (daylight saving time) was provided on a one-off basis by acts in 1923 and 1924, and then on an ongoing basis by the Summer Time Act, 1925. The 1925 act provided a default summer time period, which could be varied by ministerial order. Double summer time was considered but not introduced during the Emergency of World War II.
From 1968 standard time (GMT+1) was observed all year round, with no winter time change. This was an experiment in the run-up to Ireland's 1973 accession to the EEC, and was undone in 1971. In those years, time in Ireland was the same as in the six EEC countries, except in the summer in Italy, which switched to Central European Summer Time (CEST). One artefact of the 1968 legislation is that "standard time" (Irish: am caighdeánach) legally refers to summer time; the 1971 act defined a period of time in the winter as "winter time" and during "winter time", the time observed would be GMT, leaving "standard time" unchanged.
From the 1980s, the dates of switch between winter and summer time have been synchronised across the European Union. Possible adjustments to the Irish practice were discussed by the Oireachtas Joint Committee on Justice, Defence and Equality in November 2011, but the government stated it had no plans to change. In November 2012, Tommy Broughan introduced a private member's bill to permit a three-year trial of advancing time by one hour, to CET in winter and CEST in summer.
The statutory instruments (SIs) that have been issued under the Standard Time Acts are listed below, in format year/SI-number, and linking to the Irish Statute Database text of the SI. Except where stated, those issued up to 1967 (under the 1925 Act) were called "Summer Time Order <year>", while those issued from 1981 (under the 1971 Act) are "Winter Time Order <year>".
1926/(unnumbered), 1947/71, 1948/128, 1949/23, 1950/41, 1951/27, 1952/73, 1961/11, 1961/232 (Summer Time (No. 2) Order 1961), 1962/182, 1963/167, 1964/257, 1967/198, 1981/67, 1982/212, 1986/45, 1988/264, 1990/52, 1992/371, 1994/395, 1997/484, 2001/506
Closing time in Irish public houses is later during summer time. Between 1933 and 1961, lighting-up time was an hour before/after sunrise/sunset in summer-time, as opposed to half-an-hour in winter time. Since 1961, it has been half-an-hour in all cases. A similar change in the definition of night for aviation was made in 1967.