Western European Summer Time (WEST) is the name commonly used for the daylight saving period that advances clocks by one hour to UTC+1. It is applied in several territories in western Europe and nearby regions during the warmer months to make better use of evening daylight. The practice is a form of daylight saving time and is measured relative to Coordinated Universal Time (UTC).

Where WEST is used

The following territories use WEST when observing summer time. Local usage and legal names vary, but the practical clock offset is the same (UTC+1):

Names and local terminology

Although the offset is the same, WEST is known by different local names. In the United Kingdom it is commonly called British Summer Time (BST). Note that the abbreviation "BST" can also refer to Bangladesh Standard Time in other contexts. In the Republic of Ireland the legal summer-time name is Irish Standard Time (sometimes informally called Irish Summer Time).

Timing and transitions

The usual period for WEST runs from the last Sunday in March to the last Sunday in October. Transitions are scheduled to occur at 01:00 UTC on the relevant Sundays so that clocks jump forward or back by one hour relative to standard time. See the timing markers often described as the last Sunday in March and the last Sunday in October. Outside that interval, affected areas revert to standard time — typically Greenwich Mean Time (GMT), which is UTC+0.

History, coordination and practical notes

Daylight saving schemes like WEST originated in the 20th century to provide extra evening daylight and to align activity hours with daylight availability. In Europe, transition dates have been coordinated across many jurisdictions to simplify travel, communication and commerce. Individual countries or territories retain the authority to choose whether and how to apply summer time; for example, some places have adjusted start or end dates in response to religious observances or temporary policy changes.

Why it matters

For travelers, businesses and anyone scheduling events across borders, awareness of WEST and its local names is important to avoid confusion. Because the offset during WEST is one hour ahead of UTC, it is straightforward to convert times when coordinating with regions that remain on UTC or use other offsets. Always confirm the applicable local name and any short-term exceptions when planning activities during the transition periods.