What time is it in London, England, United Kingdom

London uses the Europe/London time zone. Greenwich Mean Time (GMT) is the standard time, at UTC+0, so a clock on GMT shows the same hour as UTC. British Summer Time (BST) is the summer time, at UTC+1, so the same clock reads one hour ahead of UTC. Right now London is on Greenwich Mean Time, UTC+0. The heading puts that offset first: UTC+0 in GMT / UTC+1 in BST. Noon on the London clock today is 12:00 UTC. 09:00 today is 09:00 UTC and 17:00 today is 17:00 UTC. The other part of the year uses British Summer Time, UTC+1 (BST). The two offsets are 60 minutes apart. UTC stays put when the civil clock changes. A London time on this offset is already a UTC time.

Clocks go forward on the last Sunday of March and back on the last Sunday of October, both at 01:00 UTC.

On Sunday 28 March 2027 at 01:00 GMT the clock becomes 02:00 BST, and the offset moves from UTC+0 to UTC+1. That instant is 01:00 UTC. Local times from 01:00 to 02:00 do not occur that morning. London, Manchester, Edinburgh, and Belfast share Europe/London, so the change is the same instant in each of them.

The change after that is on Sunday 31 October 2027, the last Sunday of October, when the clocks go back. At 02:00 BST the clock becomes 01:00 GMT. That instant is 01:00 UTC, and the offset moves from UTC+1 to UTC+0. From 01:00 to 02:00 the same clock reading happens twice, first as BST and then as GMT, so the civil day runs for 25 hours. At 00:30 UTC the clock reads 01:30 BST. At 01:30 UTC it reads 01:30 GMT. A time in that hour needs BST, GMT, or a UTC time.

Sunrise and sunset in London today are 07:08 and 16:20, and the day is 9 h 12 min long. The clock is on Greenwich Mean Time, UTC+0.