Greenwich in Greater London, England, United Kingdom — Northwestern Europe (the British Isles)

The Shepherd 24-hour Gate Clock

The Time Ball

Photographed by Michael Herrick, April 28, 2018

1. The Shepherd 24-hour Gate Clock Marker

Inscription.
The Shepherd 24-hour Gate Clock
This is one of the earliest electrically driven public clocks and was installed here in 1852. The dial always shows Greenwich Mean Time (GMT). In summer Britain converts to British Summer Time (BST), which is an hour ahead of GMT, and the clock then appears one hour 'slow'.

Being a 24-hour clock, the hour hand marks noon (XII) at the bottom of the dial and midnight (0) at the top. The time shown is accurate to 0.5 of a second.

The Time Ball
The red time ball on top of Flamsteed House is one of the world's first visual time signals. It was installed in 1833 (though the present one dates to 1919) to enable navigators on ships in the Thames to check their marine chronometers.

The Time Ball drops daily at 1300hrs (GMT in winter, BST in summer). It is raised halfway up the mast at 1255hrs as a preparatory signal and to the top 2 minutes before it drops.

Topics. This historical marker is listed in these topic lists: Industry & Commerce • Science & Medicine.

Location. 51° 28.68′ N, 0° 0.083′ W. Marker is in Greenwich, England,

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in Greater London. It can be reached from the intersection of Blackheath Avenue and Great Cross Avenue, on the left when traveling north. Located at the Royal Observatory Greenwich. Touch for map. Marker is in this post office area: Greenwich, England SE10 8XJ, United Kingdom. Touch for directions.

Regionally, this marker is in the Greater South East.

Globally, it is on the Atlantic Ocean,

in the North Atlantic Region,

in Europe,

in Atlantic Europe,

on one of the British Isles,

in the Western World,

and in the Anglosphere.

Historically, it finds itself in what was once the Roman Empire.

Other nearby markers. At least 8 other markers are within walking distance of this marker: Ordnance Survey Bench Mark (here, next to this marker); Time for everyone (a few steps from this marker); Airy’s meridian line (a few steps from this marker); Greenwich Meridian Marker, 1750-1851 (a few steps from this marker); The Greenwich Meridian Telescope (a few steps from this marker); Bradley’s meridian line (a few steps from this marker); Family Tombstone of Edmund Halley (within shouting distance of this marker); Flamsteed’s Well Telescope

The Shepherd 24-hour Gate Clock image. Click for full size.

Photographed by Michael Herrick, April 28, 2018

2. The Shepherd 24-hour Gate Clock

(within shouting distance of this marker). Touch for a list and map of all markers in Greenwich.

Also see . . . Royal Observatory, Greenwich on Wikipedia. (Submitted on May 24, 2018, by Michael Herrick of Southbury, Connecticut.)

The Flamsteed House with the Red Time Ball image. Click for full size.

Photographed by Michael Herrick, April 28, 2018

3. The Flamsteed House with the Red Time Ball

Photographed by Adam Margolis, June 16, 2026

4. The Shepherd 24-hour Gate Clock Marker

Credits. This page was last revised on July 11, 2026. It was originally submitted on May 24, 2018, by Michael Herrick of Southbury, Connecticut. This page has been viewed 842 times since then and 63 times this year. Photos: 1, 2, 3. submitted on May 24, 2018, by Michael Herrick of Southbury, Connecticut. 4. submitted on June 30, 2026, by Adam Margolis of Mission Viejo, California.