British Summer Begins 2025. This is the longest day of the year and marks the start of. On sunday 31st march, the clocks 'spring forward' by one hour, marking the annual move from greenwich mean time (gmt) to british summer time (bst).
They move forward by one hour in march, for what is known as british summer time, and turn back by one hour in october. Tables showing british summer time dates of 2025, previous and future years up to 2030.