Human Sun Clock

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The Human Sun Clock at Reveley Lodge Garden

(An analemmatic sundial)


All sundials record a shadow thrown by the sun onto a scale laid out with markings to represent the time of the day. A sundial is a form of clock. Most commonly the sundial is a small metal plate with a pointer or shadow post to make the shadow on a scale of hours, and it is often mounted on a stone plinth in a garden.

A human sundial or sun clock works in a similar way but instead uses a human being as the post to cast a shadow onto an hourly scale marked on the ground. The person casting the shadow stands on a central stone which has small rectangles laid out for each month of the year.

In this sun clock in Bushey there are two arcs of hour stones arranged around the plinth. The outer arc measures the shadow in Greenwich Mean Time (GMT) hours, and the inner arc measures summer time (BST). Because people use gardens mostly on summer sunny days, this inner arc is used more than the outer arc.

With modern watches, we take the measurement of time for granted, but to early man, the position of the sun in the sky was the main way to tell the time of day. Two times are obvious, dawn when the sun rises, and dusk when it sets. Also the highest point of the sun in the middle of the day marks out noon, and this is due South.


Because we know that the highest point of the midday sun is south and that the shadow from the sun at this point will point North, then we can find North in the daytime when bright sunlight prevents us from seeing the pole star or indeed any star, although of course they are still there. When we have found this North and South line we can then lay out a scale dividing sunrise and sunset through midday into divisions which we call hours. Because of the adjustment of our clocks in Summer Time, the midday time by the sun is called one o’clock, marked by the inner row of hour marker stones.

In our human sun clock or more correctly an analemmatic sundial, the user stands on the midline of the central plinth stone on the correct month square. If the sun is shining then his or her shadow will point to the time of day just like a traditional sundial on a plinth. He should stand on the month, and if your shadow does not reach the hour stone, then raise your arm to make the shadow. Remember to raise the arm which is nearest the midline of the standing stone.

The months on the central plinth are marked out to make the user stand on a slightly different place each month of the year. This gives a more precise reading. This sun clock has been set up to be as accurate as possible, but it will never be quite as close as a modern watch - however it will never need a battery or need to be wound up!


There are not many human sun clocks in England but there are sun clocks at Chatsworth House, Blenheim Palace, Longleat and Lincoln Castle. Also there are a number of human sun clocks in school playgrounds, which have been painted onto the ground surface. This one was constructed in 2005.


Our own sundial has been handcut in Portland Stone by Sarah Stewart-Smith, a stonemason who works in Cornwall. She lived in Bushey some years ago and attended Merry Hill Primary School.

Her work includes stonework and lettering at the Eden Project. She can be contacted through her website at:


 The calculations for setting up this sun clock to the Bushey Latitude and Longitude were provided by Douglas Hunt of Modern Sunclocks at:


Further information about sundials of all kinds can be found on the extensive website of the British Sundial Society at:


This sunclock was given in memory of Helena Hurndall

© Reveley Lodge Trust 2019, which is a company limited by guarantee (England 4772191) and a registered charity (1099935).