Ireland operates on Greenwich Mean Time (GMT) during winter months, which is Coordinated Universal Time (UTC+0). During daylight saving time, observed from the last Sunday in March to the last Sunday in October, Ireland switches to Irish Standard Time (IST), which is UTC+1.
All of Ireland follows the same timezone. Major cities including Dublin, Cork, Galway, Limerick, and Waterford all observe the same time. Ireland shares its timezone with the United Kingdom and Portugal.
Ireland is one of the few countries where the "standard" time is actually the summer time. Legally, Irish Standard Time (IST) is UTC+1, and the country switches to GMT (UTC+0) in winter as a temporary measure, making Ireland's approach to DST technically the reverse of most countries.