Greenwich Mean Time (GMT)

Current GMT Time at the Prime Meridian

The clock below tracks Greenwich Mean Time (GMT), the local time at the Royal Observatory in Greenwich, London. The United Kingdom is currently on British Summer Time (BST, UTC+1), so the GMT clock runs one hour behind UK civil time. Use this clock when you need the time at the Prime Meridian (0° longitude), the reference line from which every other time zone is calculated.

What GMT Means: The UK's Winter Time Zone

Greenwich Mean Time is UTC+0, the civil time used in the United Kingdom during winter. It is the mean solar time at the Royal Observatory Greenwich, measured from midnight.

GMT is a time zone, a region of the globe that observes the same clock time. The UK adopts GMT from late October to late March. For the rest of the calendar, the UK switches to British Summer Time (BST, UTC+1).

GMT vs BST: When Each Applies

The UK changes its clocks twice annually.

Clocks go forward (GMT → BST) on the last Sunday of March at 01:00 UTC. In 2027, that is Sunday 28 March at 01:00 local time. Clocks jump to 02:00.

Clocks go back (BST → GMT) on the last Sunday of October at 02:00 local time. In 2026, that is Sunday 25 October at 02:00 BST. Clocks fall back to 01:00 GMT.

If you see a UK time listed as "14:00 GMT" in July, it is wrong. The correct label would be "14:00 BST" or "13:00 UTC." For a full breakdown, read GMT vs BST.

GMT vs UTC: The Quick Distinction

Many people use "GMT" and "UTC" interchangeably. For most practical purposes (booking flights, scheduling calls, checking the time), treat them as the same offset: UTC+0. They are not identical.

GMT is a time zone. It is the civil time used by specific countries: the UK in winter, Iceland across all seasons.

UTC is a time standard. Coordinated Universal Time runs on atomic clocks. It does not observe daylight saving time. UTC is the reference from which all time zones are measured.

GMT relies on the Earth's rotation (solar time). UTC relies on atomic time. The difference is negligible for daily life. For precise technical work (programming, satellite operations, scientific data), use UTC. Read more in GMT vs UTC.

Countries That Use GMT All Year

Several countries and territories use GMT (UTC+0) as their standard time in every season. They do not observe daylight saving time.

Portugal (mainland) uses WET (Western European Time, UTC+0) in winter and WEST (UTC+1) in summer, on the same dates as the UK. Ireland runs on the same clock as the UK but calls summer time "Irish Standard Time" (IST). The Canary Islands and the Faroe Islands also use WET/WEST.

For a full list, read What Countries Share the Same Time Zone as the UK?

When GMT Matters Most

Scheduling a meeting with someone in London during November? GMT is the local time. Calling in July? The local time is BST, one hour ahead.

People in Iceland, Ghana, or Côte d'Ivoire use GMT all twelve months. A meeting with a colleague in Reykjavik will always be at the same GMT offset, no matter the month.

Plan your call differently if you are booking a video conference with someone in London in August versus someone in Accra in August. The Londoner will be on BST (UTC+1). The Accra contact will be on GMT (UTC+0). They are one hour apart, even though both time zone names contain "Greenwich."