Time | Royal Museums Greenwich

Greenwich Mean Time

Time before Greenwich Mean Time: the confusing case of the traveller's watch

Before time became standardised, different areas of the country all kept their own 'local time'. This gold traveller's watch with two minute hands shows how tricky that could be

Seasons and calendars

Summer and winter solstices explained

Find out how the position of the Sun determines the longest and shortest days of the year in this special Royal Observatory Greenwich Illuminates extract

Time and navigation

What is the Prime Meridian and why is it in Greenwich?

How Greenwich found its place in the centre of global time and navigation

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Greenwich Mean Time

Discover why Greenwich is known as 'the home of time'

An image of a gold watch with a large face with roman numeral numbers on it, and two watch hands

Time before Greenwich Mean Time: the confusing case of the traveller's watch

Before time became standardised, different areas of the country all kept their own 'local time'. This gold traveller's watch with two minute hands shows how tricky that could be

Mid 1900s photograph of Flamsteed House at the Royal Observatory

The Greenwich Time Lady: Ruth Belville

Discover the story behind the media sensation Ruth Belville, who brought the correct time from the Royal Observatory to London for almost 50 years.

Black and white Shepherd Gate Clock on a brick wall.

What is Greenwich Mean Time (GMT) - and why does it matter?

How did local clock time in Greenwich change the world?

The Greenwich Time Ball and one time for all

How do you know that your watch, clock or phone is telling exactly the right time? At one time, the only way was to look to the roof of the Observatory.

A crowd looking at the Shepherd Gate Clock on a brick wall.

British Summer Time (BST) and Daylight Saving - understanding UK time changes

Why does UK time change, and when was British Summer Time first introduced? Explore the history of BST and daylight saving

Clocks and timekeeping

Read all about the history of timekeeping and the amazing instruments in Royal Observatory Greenwich's collection

A black clock face with yellow hands and numbers round the dial

When do the clocks go back?

Marking the end of British Summer Time, the clocks go back in October, giving us an extra hour in bed

Painting of HMS Erebus stuck in the ice.

The lost chronometer: the timepiece that sailed with Charles Darwin and Sir John Franklin

Learn more about the marine chronometer that journeyed on board HMS Beagle before being lost at sea during Sir John Franklin's disastrous expedition

Time before Greenwich Mean Time: the confusing case of the traveller's watch

Before time became standardised, different areas of the country all kept their own 'local time'. This gold traveller's watch with two minute hands shows how tricky that could be

Drone Photography of Royal Observatory Greenwich

The BBC pips: the Royal Observatory and the Greenwich Time Service

Discover the story behind the Greenwich time pips, first broadcast by the BBC 100 years ago in 1924

What is a nocturnal?

Learn more about the nocturnal or ‘nocturlabe’, used for centuries to tell the time based on the movement of the stars

The Greenwich Time Lady: Ruth Belville

Discover the story behind the media sensation Ruth Belville, who brought the correct time from the Royal Observatory to London for almost 50 years.

A woman wearing blue surgical gloves examines a historic clock during conservation work in the Royal Observatory's Octagon Room

When do the clocks go forward?

Marking the start of British Summer Time, the clocks 'spring forward' in March, meaning we'll lose an hour's sleep

Which years are leap years and can you have leap seconds?

Because the Earth takes a little over 365 days to orbit the Sun, we need to make adjustments to keep the seasons from drifting: leap years and even leap seconds

Why 12 months in a year, seven days in a week or 60 minutes in an hour?

While days and years are (fairly) neat astronomical events, what explains months, weeks, hours and minutes?

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Royal Observatory Greenwich is Britain’s oldest purpose-built scientific institution. Founded in 1675, it is the birthplace of modern astronomy and the home of Greenwich Mean Time.

Seasons and calendars

Keeping track of time helps us make sense of our world. Explore how people around the world divide time and mark the changing years

The Royal Observatory and Planetarium buildings seen from above during Autumn

What and when is the autumnal equinox?

When is the autumnal equinox, what date does the autumnal equinox fall on and when does summer end?

Lunar new year dates and animals of the zodiac

Find out more about the new year festival celebrated by people across Asia

Composite image showcasing the motion of the Sun between the Summer and Winter Solstices

Summer and winter solstices explained – how the Sun determines the longest and shortest days of the year

Find out how the position of the Sun determines the longest and shortest days of the year in this special Royal Observatory Greenwich Illuminates extract

When does spring start?

Did you know there are actually three main definitions for the start of spring?

A red and yellow envelope made by folding. A small ox is drawn on the front.

How to make a Hongbao for the New Year

Create your own hongbao, using origami techniques, to celebrate the New Year.

Three lucky fish posters. Each is a red diamond with a pair of yellow or gold fish.

How to make a lucky fish poster for Lunar New Year

Create a lucky fish poster to decorate your home for Lunar New Year.

How do people celebrate Chinese New Year?

What happens during Chinese New Year? The Newham Chinese Association explain some of the traditions, festivals and customs that take place when Chinese New Year is celebrated.

Image of a silhouette of a bridge in Hong Kong with orange and yellow sunset sky behind it, the Sun appears to be sitting on the water and the bottom of it is distorted in a mirage

Summer solstice

When - and what - is the summer solstice?

When is the winter solstice? The shortest day

When is the winter solstice this year? What does it mean? Is it the shortest or longest day?

Time and navigation

How are measuring time and measuring distance linked? Why is the Prime Meridian in Greenwich? Learn more about the links between time, navigation and astronomy

The lost chronometer: the timepiece that sailed with Charles Darwin and Sir John Franklin

Learn more about the marine chronometer that journeyed on board HMS Beagle before being lost at sea during Sir John Franklin's disastrous expedition

Early charts from the Mediterranean

The Caird Library and Archive’s display case highlighted three colourful charts from the rich cartographic collection of Royal Museums Greenwich.

True north and magnetic north: what's the difference?

In September 2019, for the first time in over 360 years, compasses at Greenwich pointed true north. But what does this mean - and haven't compasses always pointed 'north'?

What is longitude?

Find out what longitude is and what makes it so hard to measure

What made the search for longitude so important?

Why did most of the great European powers offer huge rewards for a way to determine longitude at sea?

Longitude found: Nevil Maskelyne and the lunar method

Find out how the celebrated Astronomer Royal helped to solve the longitude problem

Longitude found - the story of Harrison's Clocks

Who was John Harrison, and how did his clocks help to solve the problem of finding longitude at sea?

A close up of a woman's feet as she walks along the Prime Meridian Line in Greenwich, the line marking Greenwich Mean Time

What is the Prime Meridian and why is it in Greenwich?

How Greenwich found its place in the centre of global time and navigation

Meridian astronomy

Meridian astronomy is the meticulous surveying of the stars so that positions and movements of stars can be known accurately.

A timeless gift

Royal Museums Greenwich is a charity, and we rely on your support to care for our collections and help everyone appreciate the history of time and the Royal Observatory. Donate today and help shape the Museum's future

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Time before Greenwich Mean Time: the confusing case of the traveller's watch

Summer and winter solstices explained

What is the Prime Meridian and why is it in Greenwich?

Time to subscribe?

Time before Greenwich Mean Time: the confusing case of the traveller's watch

The Greenwich Time Lady: Ruth Belville

What is Greenwich Mean Time (GMT) - and why does it matter?

The Greenwich Time Ball and one time for all

British Summer Time (BST) and Daylight Saving - understanding UK time changes

When do the clocks go back?

The lost chronometer: the timepiece that sailed with Charles Darwin and Sir John Franklin

Time before Greenwich Mean Time: the confusing case of the traveller's watch

The BBC pips: the Royal Observatory and the Greenwich Time Service

What is a nocturnal?

The Greenwich Time Lady: Ruth Belville

When do the clocks go forward?

Which years are leap years and can you have leap seconds?

Why 12 months in a year, seven days in a week or 60 minutes in an hour?

Watch

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What and when is the autumnal equinox?

Lunar new year dates and animals of the zodiac

Summer and winter solstices explained – how the Sun determines the longest and shortest days of the year

When does spring start?

How to make a Hongbao for the New Year

How to make a lucky fish poster for Lunar New Year

How do people celebrate Chinese New Year?

Summer solstice

When is the winter solstice? The shortest day

The lost chronometer: the timepiece that sailed with Charles Darwin and Sir John Franklin

Early charts from the Mediterranean

True north and magnetic north: what's the difference?

What is longitude?

What made the search for longitude so important?

Longitude found: Nevil Maskelyne and the lunar method

Longitude found - the story of Harrison's Clocks

What is the Prime Meridian and why is it in Greenwich?

Meridian astronomy

Discover more from the 'Home of Time'

A timeless gift