Current Time in London

Where the world's clocks start

Every time zone on Earth is defined as an offset from a single reference point: the Prime Meridian, running through the Royal Observatory in Greenwich, a few miles from central London. That wasn't inevitable — it was decided at the International Meridian Conference of 1884, where delegates from 25 countries voted to use Greenwich as the zero-degree line for global timekeeping, largely because most of the world's shipping already used British nautical charts. London's own local time became, by that vote, the anchor every other city's offset is measured against.

The wartime experiment with double summer time

Britain's relationship with clock changes has been more radical than most. During the Second World War, the country ran on "British Double Summer Time" — clocks two full hours ahead of GMT each summer, with a one-hour offset kept even through winter — to squeeze extra daylight out of the working day for wartime production. A similar experiment ran from 1968 to 1971, keeping BST year-round to test whether abolishing the autumn clock change entirely would help road safety. Both experiments were eventually reversed, leaving the twice-yearly change we still use today.

Time differences from London

London sits close to the middle of the pack for clock changes, so most of the swings below come from the other city moving, not London.

The EU and UK still don't always flip their clocks on the exact same weekend as the US, which is why the New York gap briefly narrows rather than staying fixed at five hours.

Working hours and when to call

Most London offices run a fairly standard 9:00 to 17:30 day, with the City's financial firms often starting earlier to overlap with Asian markets closing.

• From continental Europe: full overlap all day — London sits within an hour of most of the EU.
• From the US East Coast: London's morning is New York's very early morning; a London afternoon call (14:00–17:00) lands late morning in New York.
• From the US West Coast: London's morning is the middle of the LA night; the workable window is London afternoon into LA's early morning.
• From East Asia: almost no overlap; a London morning call lands in the evening in Tokyo or Shanghai.

Bank holidays cluster in spring (Easter, early May, late May) and can catch overseas colleagues off guard since the UK's public holiday calendar doesn't match the US or EU.

Daylight through the year

At roughly 51.5°N, London sits far enough north that daylight swings dramatically across the year — from under 8 hours around the December solstice to nearly 16 hours and 40 minutes around the June solstice. That's a wider swing than New York or Tokyo see at their lower latitudes, which is part of why the UK's debate over keeping BST year-round keeps resurfacing: a London winter afternoon can turn dark before 4:00 p.m.

The ball that beat the pips by a century

Long before radio existed, London already had a way to broadcast the exact time. Since 1833, a bright red ball on a mast atop the Royal Observatory in Greenwich has risen to the top of its pole each day and dropped precisely at 1:00 p.m., timed by the Observatory's own master clocks. Ships anchored on the Thames used telescopes to catch the drop and set their marine chronometers accordingly — accuracy that mattered enormously for navigation, since a chronometer error of a few seconds could translate into miles of error at sea. The idea proved so useful that time balls spread to ports around the world, but Greenwich's was among the first, and it's still dropped daily today, largely as a heritage piece rather than a navigational necessity.

The clock regulated by pocket change

The Great Clock of Westminster, whose Great Bell gave the whole tower the nickname Big Ben, has run since 1859 with a strikingly simple calibration trick. A small stack of pre-decimal penny coins sits on top of the pendulum; adding one penny shifts the clock's rate by roughly two-fifths of a second per day, removing one has the opposite effect. Clockkeepers still use this method to keep the mechanism accurate to within about a second or two. Its chimes have been broadcast on BBC radio since 1923, and the separate "Greenwich Time Signal" — six pips marking the seconds before each hour, introduced in 1924 — is one of the longest-running time signals in broadcast history, generated for decades directly from clocks at the Observatory the pips are named for.

How we calculate this page: the live clock and UTC offset above are read directly from the IANA Europe/London time zone data via your browser, not hard-coded. Sunrise, sunset, solar noon, and twilight times are computed from London's exact coordinates (51.5072°N, 0.1276°W) using standard solar position formulas, recalculated on every page load. Moon phase is derived from the current synodic month. Airport distances use the great-circle formula from those same coordinates to each airport's published location.