Western European Summer Time

Western European Summer Time (WEST) is a summer daylight saving time scheme, 1 hour ahead of Coordinated Universal Time. It is used in the following places:

• the Canary Islands
• Portugal (including Madeira but not the Azores)
• Ireland
• the United Kingdom
• the British Crown dependencies
• the Faroe Islands

Western European Summer Time is also known locally, in the countries concerned, as:

• British Summer Time (BST) in the United Kingdom.
• Irish Standard Time (IST) (Am Caighdeánach na hÉireann (ACÉ)) in Ireland. Also sometimes erroneously referred to as "Irish Summer Time" (Am Samhraidh na hÉireann).

The scheme runs from the last Sunday in March to the last Sunday in October each year. At both the start and end of the schemes, clock changes take place at 01:00 UTC. During the winter, Greenwich Mean Time (UTC+0) is used.

The start and end dates of the scheme are somewhat asymmetrical in terms of daylight hours: the vernal time of year with a similar amount of daylight to late October is mid-February, well before the start of summer time. The asymmetry reflects temperature more than the length of daylight.

Ireland does not observe a summer time, but rather observes Standard Time during the summer months and changes to UTC+0 during the winter time period. However, as Ireland's winter time period begins on the last Sunday in October and finishes on the last Sunday in March, the result is the same.