TL;DR: London is on Greenwich Mean Time (UTC+0) in winter and British Summer Time (UTC+1) from late March to late October. So “what time is it in London” has two answers depending on the date, and the gap with most of the world changes twice a year. If you need the current time, check a live clock rather than a fixed offset.
The two seasons, and the dates that shift
The UK observes daylight saving, so London’s offset from UTC changes annually.
British Summer Time begins on the last Sunday in March, when clocks go forward at 1 a.m. to 2 a.m., and ends on the last Sunday in October, when they go back. From late October to late March, London is on GMT, UTC+0.
Those two dates are the ones that break recurring meetings. A standing 9 a.m. call that works in January shifts by an hour in July, and shifts again in October, unless both sides observe the same schedule.
Converting from common time zones
These gaps are correct during the northern winter, when London is on GMT:
- New York: London is 5 hours ahead
- Los Angeles: London is 8 hours ahead
- Berlin and Paris: London is 1 hour behind
- Dubai: London is 4 hours behind
- India: London is 5.5 hours behind
- Beijing and Singapore: London is 8 hours behind
- Sydney: London is 11 hours behind
During British Summer Time, each of those gaps shrinks by one hour, except for regions that also change at the same moment. Because the UK and the rest of Europe switch on different dates, there is a short window each spring and autumn when London is one hour off from Berlin and Paris.
Why the offset is a trap
If you memorise “London is UTC+0,” you will be an hour wrong for roughly seven months of the year. That is the majority of the year, which makes the simple version of the fact actively unhelpful.
The same applies to any region with daylight saving, and the problem compounds when two regions with different rules are involved. The reliable approach is to use the named zone, Europe/London, in any calendar or scheduling software, because the rule travels with the date.
For a live answer, a live clock showing current local time avoids the arithmetic entirely and is the better option when you just need to know what time it is right now.
What GMT actually means
Greenwich Mean Time is a time standard based on the mean solar time at the Royal Observatory in Greenwich, which sits on the prime meridian. It became the reference for world time because of the UK’s role in maritime navigation and the adoption of the meridian at the International Meridian Conference in 1884.
Strictly, the modern standard is UTC, which is based on atomic clocks and is not exactly the same as GMT. The difference is under a second in practice and irrelevant for daily use, which is why the terms are used interchangeably in ordinary conversation.
Where the distinction matters is technical: aviation, computing, and scientific timing use UTC, and “GMT” in those contexts is a colloquial label.
London versus the rest of the UK
For timekeeping purposes, London and the rest of the United Kingdom share one time zone. There is no regional variation and no equivalent of the multi-zone confusion found in the United States or Australia.
What does vary is sunrise and sunset. In midsummer, London has daylight well past 9 p.m., while northern Scotland can be light until nearly midnight. That is latitude, not time zone, and it surprises visitors who expect the clock to match the sky.
Practical scheduling advice
Three habits prevent most London scheduling errors.
Store the time in the local zone of the meeting owner. If the organiser is in London, set the meeting as Europe/London and let the software convert for everyone else.
Check the week of the switch. If a recurring meeting falls within a week of the last Sunday in March or October, confirm the time explicitly rather than trusting the automation.
Avoid quoting abbreviations. “BST” and “GMT” are clearer than a bare offset, but a city name plus the date is clearer still, because it removes any ambiguity about which rule applies.
Why London is the reference point it is
London’s timekeeping prominence is not accidental. The Royal Observatory at Greenwich was established in 1675 to solve the longitude problem for navigation, and the meridian passing through it became the world’s reference line in 1884. Railway time in Britain standardised the country on GMT in the 1840s, decades before most other countries standardised at all.
That history is why the prime meridian runs through London rather than Paris, Washington, or Berlin, and why GMT became the lay term for the world’s zero offset. It is also why British Summer Time exists: the campaign to shift clocks for evening daylight was advocated in Britain in the early twentieth century and adopted during the First World War to save coal.
None of that changes the practical answer, but it explains why a single city carries a concept that the rest of the world uses daily.
The short answer
London is UTC+0 in winter and UTC+1 in summer, switching on the last Sundays of March and October. For a specific date, use the named zone or a live clock. For a recurring meeting, assume the gap changes twice a year and check it.