UK and Ireland Time: Same Clocks, Different Names

Both countries use Greenwich Mean Time in winter and one hour ahead in summer, and both change their clocks at the same moment, 01:00 UTC on the last Sundays of March and October.

In the UK, summer time is called British Summer Time, BST. In the Republic of Ireland it is called Irish Standard Time, IST, which is also the abbreviation for India Standard Time and Israel Standard Time. The result is that a confusing abbreviation can hide the fact that nothing changes.

Irish law treats the summer clock as the 'standard' time and the winter clock as a negative offset, a technicality that has no practical effect.