Visit the home of time

Visit the home of Greenwich Mean Time and discover how time-keeping, astronomy, global exploration and world communications are all intricately linked.

Take time to stand astride the world-famous Prime Meridian, watch the iconic Time Ball drop, set your watch to the first public clock to show GMT, and admire John Harrison's intricate timepieces in the Royal Observatory. All have been instrumental to the world we know today. 

Stand astride the Prime Meridian Line


Greenwich Meridian Line

Greenwich is the historic home of the Prime Meridian Line – Longitude 0º. It has served as the reference line for Greenwich Mean Time (GMT) since 1884. Stand astride the line – with a foot in each hemisphere – to take in the wonder of the solar system, time-keeping and our globalised world while enjoying spectacular views of the City of London and the Thames. Or visit after-dark to see the symbolic green laser that beams out northwards along the Meridian Line.

It’s easy to take the standardised time system for granted, but it’s actually a relatively new development. Before the 1850s, precision time-keeping was only really a concern to astronomers and sailors and there were no national or international conventions on how time should be measured or when the day would begin and end.

With the vast expansion of the railway and communications networks, the worldwide need for an international time standard became imperative, and Greenwich was chosen as the centre for world time.

Visit the Prime Meridian Line

Watch the Time Ball drop at Flamsteed House


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The bright red Time Ball on top of Flamsteed House – the oldest of the Royal Observatory buildings – is one of the world's earliest public time signals. Created in 1833, it was used to distribute time to ships on the Thames and to many Londoners. Still in operation today, it’s a fascinating reminder of the drive towards a standardised time system for Great Britain and then the world.

Stand outside Flamsteed House on any day of the week to watch the Time Ball rising halfway up its mast at 12.55pm. At 12.58pm it rises all the way to the top. At 1pm exactly, the ball falls, providing a time signal to anyone who happens to be looking. Please note: the time ball will not operate if the weather is too windy.

See the Time Ball drop

Set your watch to the Shepherd gate clock


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Installed at the gates to the Royal Observatory, the iconic Shepherd gate clock was the first clock ever to show Greenwich Mean Time (GMT) directly to the public. Set your watch to the clock and ponder what it was like before time became standardised.

The clock is a ‘slave dial’ connected to the Shepherd master clock. This was once the heart of Britain's time-distribution system, which sent the time by telegraph wire to London, Edinburgh, Dublin and many other cities, and, from 1866, to Harvard University in Cambridge, Massachusetts via the new transatlantic submarine cable. In terms of the distribution of accurate time into everyday life, it’s one of the most important clocks ever made.

When timekeeping first became standardised, some people in London made businesses from it. The best known example is Ruth Belville, known as the Greenwich Time Lady. Belville’s father, John Henry Belville, worked at the Royal Observatory and set his watch to GMT there every morning. The family would then ‘sell’ the time to clients who subscribed to their service by setting their clocks for them.

Own a replica of the Shepherd gate clock

Admire John Harrison’s timekeepers at the Royal Observatory


John Harrison's marine timekeeper H1 dial

Did you know that the history of timekeeping and navigation are intricately linked? Pay a visit to John Harrison's 18th-century precision timepieces, H1, H2, H3 and H4 – on display in the Royal Observatory – to bring this thought tick-tocking into life.

The carpenter-turned-clockmaker cracked a problem that had baffled astronomers and mathematicians for centuries. His portable inventions revolutionised maritime exploration and trade by allowing ships to determine longitude at sea, which drastically reduced the risk of getting lost.

See the Harrison clocks