The Prime Meridian at Greenwich, London is the reference for every time zone in the world.
What is Greenwich Mean Time (GMT)?
United Kingdom is now on GMT
All-year British Summer Time (BST) was in force from February 1968 until October 1971.
Read more about the "British Experiment" and the history of BST in this article.
When BST starts, at 01:00 GMT - clocks go forward one hour. When BST ends, clocks go back one hour to GMT