Irish Standard Time

Frequently asked questions

Common questions about IST, daylight saving, and how to handle it in software. Can't find what you need? Email [email protected].

Why does Ireland have its own timezone code (IST) when it shares the same clocks as the UK for part of the year?

Ireland uses the acronym IST for Irish Standard Time during summer, distinguishing its time zone path legally and technically from British Summer Time (BST), even though both Dublin and London show the same UTC+01:00 during the summer months.

Is Irish Standard Time the same as India Standard Time?

They share the abbreviation IST but are completely different: Ireland IST is UTC+01:00 in summer, while India Standard Time (also commonly abbreviated IST) is UTC+05:30 year-round with no daylight saving.

When does Irish Standard Time end each year?

On the last Sunday of October at 02:00 IST, clocks go back to 01:00 Greenwich Mean Time (UTC+00:00), marking the end of summer time in Ireland.

When does Daylight Saving Time start in Ireland?

Dublin springs forward on the last Sunday of March, moving clocks from 01:00 GMT to 02:00 IST, and keeps the extra evening light until October.

Does all of Ireland observe Daylight Saving Time?

Yes. The entire island of Ireland, including Northern Ireland (which follows UK BST), uses the same shift schedule, so Dublin and Belfast are always in lockstep.

Why does Ireland change clocks at 01:00/02:00 GMT instead of midnight?

The last Sunday of March and October overnight change minimizes disruption to businesses, travel, and TV programming because most people are asleep when it happens.

How does Irish Standard Time affect meeting planning with the United States?

Dublin is 5 hours ahead of the US East Coast for most of the year, both in summer (UTC+01:00 vs UTC-04:00) and in winter (UTC+00:00 vs UTC-05:00). For two to three weeks in March and one week from late October to early November, when the US and Ireland change clocks on different dates, the gap is 4 hours.

Can two different IST times appear on a meeting invite?

Yes—some calendar systems reinterpret IST as India Standard Time, so clarify 'Dublin time' or 'Irish time' to avoid showing the wrong hour to colleagues in Asia or Europe.

Why does the Irish time zone go backwards?

Ireland doesn't go backwards; it transitions from Irish Standard Time back to Greenwich Mean Time (its winter time), which simply brings it back in line with UTC+00:00—the base offset for the Greenwich meridian.