A report on Greenwich and Greenwich Mean Time

Old Royal Naval College and University of Greenwich buildings on the bank of the River Thames
Greenwich clock with standard measurements
Prehistoric burial mounds in Greenwich Park
Clock in Kumasi, Ghana, set to GMT.
Adriaen van Stalbemt's A View of Greenwich, c. 1632, showing King Charles I (in the black hat) and his family. Royal Collection, London.
In the 1880s, if this place is so cut into three: east, central and west zones of about 30,000 inhabitants each, the central one had less than 10% recognisable poverty, the minimum of London's map above, but the others (east and west) more than 40%.
The former Greenwich Town Hall, now known as "Meridian House"
A map showing the wards of Greenwich Metropolitan Borough as they appeared in 1916.
Boats at Greenwich at the end of the Great River Race
The Royal Navy Type 45 destroyer moored on the riverfront at Greenwich in 2015
Trinity Hospital, Greenwich
Spiral staircase and lantern at the Queen's House in Greenwich
Town centre
Greenwich Market
Millennium Leisure Park
Royal Observatory with the time ball atop the Octagon Room
Pepys Building
Greenwich station

Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, counted from midnight.

- Greenwich Mean Time

Greenwich is notable for its maritime history and for giving its name to the Greenwich Meridian (0° longitude) and Greenwich Mean Time.

- Greenwich
Old Royal Naval College and University of Greenwich buildings on the bank of the River Thames

5 related topics with Alpha

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World map of current time zones

Coordinated Universal Time

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Primary time standard by which the world regulates clocks and time.

Primary time standard by which the world regulates clocks and time.

World map of current time zones
Graph showing the difference DUT1 between UT1 and UTC (in seconds). Vertical segments correspond to leap seconds.

It is effectively a successor to Greenwich Mean Time (GMT).

On electronic devices which only allow the time zone to be configured using maps or city names, UTC can be selected indirectly by selecting cities such as Accra in Ghana or Reykjavík in Iceland as they are always on UTC and do not currently use Daylight Saving Time (which Greenwich and London do, and so could be a source of error).

Standard time zones of the world (February 2021). The number at the bottom of each zone specifies the number of hours to add to UTC to convert it to the local time.

Universal Time

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ERA = 2π(0.7790572732640 + 1.00273781191135448Tu) radians

ERA = 2π(0.7790572732640 + 1.00273781191135448Tu) radians

Standard time zones of the world (February 2021). The number at the bottom of each zone specifies the number of hours to add to UTC to convert it to the local time.
An 1853 "Universal Dial Plate" showing the relative times of "all nations" before the adoption of universal time

Starting in 1847, Britain established Greenwich Mean Time, the mean solar time on the Prime Meridian at Greenwich, England, to solve this problem: all clocks in Britain were set to this time regardless of local solar noon.

Time zones of the world

Time zone

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Area that observes a uniform standard time for legal, commercial and social purposes.

Area that observes a uniform standard time for legal, commercial and social purposes.

Time zones of the world
Time zones of the world
Plaque commemorating the Railway General Time Convention of 1883 in North America
The control panel of the Time Zone Clock in front of Coventry Transport Museum
1913 time zone map of the United States, showing boundaries very different from today
World map of time zones in 1928
Difference between sun time and clock time during daylight saving time:

The Royal Observatory, Greenwich, founded in 1675, established Greenwich Mean Time (GMT), the mean solar time at that location, as an aid to mariners to determine longitude at sea, providing a standard reference time while each location in England kept a different time.

It was based on longitude 172°30′ east of Greenwich, that is 11 hours 30 minutes ahead of GMT.

In 1300, the City was still confined within the Roman walls.

London

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Capital and largest city of England and the United Kingdom, with a population of just over 9 million.

Capital and largest city of England and the United Kingdom, with a population of just over 9 million.

In 1300, the City was still confined within the Roman walls.
The Lancastrian siege of London in 1471 is attacked by a Yorkist sally.
Westminster Abbey, as seen in this painting (by Canaletto, 1749), is a World Heritage Site and one of London's oldest and most important buildings.
Map of London in 1593. There is only one bridge across the Thames, but parts of Southwark on the south bank of the river have been developed.
The defensive Lines of Communication, planned during the English Civil War, c. 1643, surrounded The City, Westminster, Southwark, Lambeth and related areas (Vertue, 1738).
The Great Fire of London destroyed many parts of the city in 1666.
View to the Royal Exchange in the City of London in 1886
Arms of the Corporation of the City of London: Argent, a cross gules in the first quarter a sword in pale point upwards of the last; Supporters: Two dragons with wings elevated and addorsed argent on each wing a cross gules; Crest: On a dragon's wing displayed sinister a cross gules
Satellite view of London in June 2018
London from Primrose Hill
The Tower of London, a medieval castle, dating in part to 1078
Trafalgar Square and its fountains, with Nelson's Column on the right
Modern styles juxtaposed with historic styles; 30 St Mary Axe, also known as "The Gherkin", towers over St Andrew Undershaft
A fox on Ayres Street, Southwark, South London
Population density map
The City of London, one of the largest financial centres in the world
The London Stock Exchange at Paternoster Square and Temple Bar
A view from Westminster Millennium Pier on the River Thames, December 2018
Journeys in Greater London by mode from 1997 to 2018
Heathrow Airport is the busiest airport in Europe as well as the second busiest in the world for international passenger traffic. (Terminal 5C is pictured.)
The London Underground is the world's oldest and third-longest rapid transit system.
St Pancras International is the main terminal for high-speed Eurostar and High Speed 1 services, as well as commuter suburban Thameslink and inter-city East Midlands Railway services.
A red double-decker bus
Santander Cycle Hire near Victoria in Central London
Imperial College London, a technical research university in South Kensington
King's College London, established by Royal Charter in 1829, is one of the founding colleges of the University of London.
The front façade of the Royal College of Music
Piccadilly Circus
Harrods in Knightsbridge
Scene of the annual Notting Hill Carnival, 2014
Shakespeare's Globe is a modern reconstruction of the Globe Theatre on the south bank of the River Thames.
Sherlock Holmes Museum in Baker Street, bearing the number 221B
Keats House, where Keats wrote his Ode to a Nightingale. The village of Hampstead has historically been a literary centre in London.
Aerial view of Albertopolis. Albert Memorial, Royal Albert Hall, Royal Geographical Society and Royal College of Art are visible near the top; Victoria and Albert Museum and Natural History Museum at the lower end; Imperial College, Royal College of Music, and Science Museum lying in between.
The Royal Albert Hall hosts concerts and musical events.
The Horse Ride is a tree tunnel (route overhung by trees) on the western side of Wimbledon Common.
Aerial view of Queen Elizabeth Olympic Park, home of the 2012 Summer Olympics
Wembley Stadium, home of the England football team, has a seating capacity of 90,000. It is the UK's biggest stadium.
10 Downing Street, official residence of the Prime Minister
The West End theatre district in 2016
The Bank of England, established in 1694, is the model on which most modern central banks are based.
The east wing public façade of Buckingham Palace was built between 1847 and 1850; it was remodelled to its present form in 1913.
Broadcasting House in central London, headquarters of the BBC
St Mary's Hospital, a constituent of Imperial College School of Medicine, where in 1928 Alexander Fleming discovered penicillin in the second floor laboratory.
A New Routemaster (which replaced the AEC Routemaster) entered service in 2012. The red double-decker bus is an emblematic symbol of London.
Comptons of Soho during London Pride in 2010
The hackney carriage (black cab) is a common sight on London streets. Although traditionally black, this is not a requirement with some painted in other colours or bearing advertising.
Opened in 1937, the Odeon cinema in Leicester Square hosts numerous European and world film premieres.
The Royal Albert Hall hosts concerts and musical events, including The Proms which are held every summer.
Abbey Road Studios was given grade II listed status for its "cultural and historical importance" in 2010.
Hyde Park (with Kensington Gardens in foreground) has been a popular public space since it opened in 1637

London has four World Heritage Sites: the Tower of London; Kew Gardens; the combined Palace of Westminster, Westminster Abbey, and St Margaret's Church; and also the historic settlement in Greenwich, where the Royal Observatory, Greenwich defines the Prime Meridian (0° longitude) and Greenwich Mean Time.

Finding Greenwich time while at sea using a lunar distance. The lunar distance is the angle between the Moon and a star (or the Sun). The altitudes of the two bodies are used to make corrections and determine the time.

Lunar distance (navigation)

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Angular distance between the Moon and another celestial body.

Angular distance between the Moon and another celestial body.

Finding Greenwich time while at sea using a lunar distance. The lunar distance is the angle between the Moon and a star (or the Sun). The altitudes of the two bodies are used to make corrections and determine the time.

The lunar distances method uses this angle, also called a lunar, and a nautical almanac to calculate Greenwich time if so desired, or by extension any other time.

In celestial navigation, knowledge of the time at Greenwich (or another known place) and the measured positions of one or more celestial objects allows the navigator to calculate latitude and longitude.