Time over the wires

This combined galvanometer and 24 hour clock was in the window of a shop called Hancocks, somewhere in London in the early 20th century.


It was one of many clocks that were electrically connected to London’s Greenwich Observatory. This service started in the 1850s, when Greenwich time was first provided to interested subscribers – the watchmakers, government offices, and railway operators who needed to know the exact time. In 1873, the cost of connecting your apparatus to the nearest Post Office’s time server was ¬£12 a year.

I suppose the needle would have deflected at the start of each hour. More ingenious solutions were tried to indicate the exact moment: most popular was a ball on a pole, that descended at the start of the new hour.

Sometimes, though, nothing can beat a personal service. This picture shows Ruth Belville, the Greenwich Time Lady. Her job was to set her accurate pocket watch at the main Greenwich Observatory 24 hour clock on a Monday morning, get a signed certificate from an official, and then walk around London visiting forty or fifty chronometer makers, who would then transfer the right time to their own most reliable timekeeper. She carried on doing this job from 1892 to the 1930s.


This morning, my computer asked one of Apple’s computers on the other side of the world for the right time, using the Network Time Protocol to set its clock, taking less than a few seconds to do it. Just some of the everyday magic that we take for granted today.


To qualify, just make one of these

If you wanted to qualify as a master clockmaker in 17th century Augsburg (Germany), your final assignment was to make a clock with the following specifications:

A clock which shows the time both in the great and small clock ie the 24 hour and 12 hour system. It should show the times of sunrise and sunset and also show the position of the sun and moon in the zodiac throughout the year. It should strike the quarter hours and the full hours in both 1-12 and 1-24 hour systems.

You would be given about six months to make one and submit it to the examiners, the guild masters. If it was good enough, you became a master clockmaker. The examiners would be expecting something like this, perhaps:


This example of a masterpiece clock organizes its myriad features around a hexagonal framework. On two faces there are main dials showing the time in the ‘Great’ (24 hour) system. On a face not visible here, there are hands showing the age and phase of the moon, and an astrolabe with sky map. The large dial shown here has five sets of numbers, and a moving sunrise/sunset/daylight indicator formed by two light and dark moving discs. Another hour hand shows either Nuremberg hours (where counting started at sunset) or Bohemian hours (where counting started at sunrise). And around the outside you can tell the time in both the Great and Small systems.

Other dials show the day of the week, and control the bell-ringing. There’s a switch to choose 24 hour or 12 hour striking, so that 13 o’clock can be indicated either by 1 or 13 chimes. And on the right dial below there’s a read-out of the current state of the count wheels for the chiming – notice how the gaps between the numbers are proportional to them, with wider gaps for the large numbers. This is the clockmaker’s ingenious solution to the task of keeping count of how many chimes to make.


This clock’s intriguing because it provides for a number of different and conflicting time standards, even at the risk of increasing its complexity. To some extent this might be because the clock is an academic exercise, rather than a cost-effective market-ready offering, but it suggests that both Nuremberg and Bohemian hours were still in use around 1650.

I hope the maker of this example qualified!

You can see this clock in the British Museum, London. It also appears in a new book, Clocks, by David Thompson, published in 2004 by the British Museum Press. The book describes some of the treasures in the Museum’s clocks department, with many fine photographs by Saul Peckham.

Mystery clock

I spotted this strange clock recently, and I thought it would be fun to make it a mystery picture. Where can you see this clock? (Sorry about the quality.)


No prizes for guessing the answer, except the satisfaction of being a clock wizard!

In the Navy

This is a solid-looking clock for the seafarer in your life, from Chelsea Clocks.


The TimeMaster’s 8 day mechanical movement is the finest in the world, according to Chelsea Clocks, so you should expect to pay 00 for one of these. Please buy me one!

Venice clock

Here’s a good picture of a 24 hour analog clock in Venice.


Andy took this photo, and says:

…a clock just over the Rialto bridge. There is a flea market around you but if you turn and look up, there it is. Very strange as the hours don’t start/end where you would expect. I heard a strange story about this clock… I was told that the Venetians used to re-set the clock every day. When the sun rose, it was six o’clock. So at dawn, the clock was set to six. And that is where the clock sits now. It doesn’t run, or at least it wasn’t when I was there. Do you know if there is any truth to this?

Ryan’s clock

Ryan Provost emails:

I created a 24-hour analog clock this weekend. The clock also has a metric time dial (in 1/100 day), and a 40-hour dial (because there’s 400 gradients in a full circle, 100 grads per 1/4 circle). All I need is a clock mechanism kit, and a AA battery, and to set the time, and I’m gonna show it to everybody!


Looks like an nice design.

Swedish clocks

From Sweden, Sylvie emails to tell us about her work with 24 hour clocks:

In Sweden we have been developing new ways for people with development disorder to handle their everyday activities. A very difficult field is to handle time. Time is hard to get a grip on when you are not able to think abstract or have trouble making a plan in your mind. It’s too many thinking activites involved at the same time. In Sweden we have developed several technical aids and some methods to help simplify handling time issues. One of these are 24 hour clocks.Unfortunately we do not have home sites in English that describe our work with this.

The best site to get to know what we are dealing with is You can click below the clock icon on Tidshjalpmedel. Now there is a menu where you will find the Swedish word dygnsklocka which means 24 clock.


There are three models right now. The first one was developed in the northern region of Sweden where it hardly ever gets dark in the summer time. This created lots of trouble for people with thinking difficulties. A man who worked at a daycare center developed it to help some of his mates. Now they are selling it. It’s called Pajalaklockan after the village. It has plastic bits for every half hour that you can put messages, symbols on, and they come in different colours making it possible to mark the working hours in different colours from freetime and sleeping time.

Star time

I’ve been looking at the Zeitladen site and, being far from fluent in German, I can’t decide whether they’re selling standard 24 hour clocks and watches or sidereal (sternzeit or star time) versions.

If you watch a particular star and make a note of when it is highest in the sky (its transit time) on two successive days, you’ve measured a sidereal day. A sidereal day is about 23 hours and 56 minutes.

If you set two clocks, one showing sidereal time, the other 24 hour time, to tell the same time as each other, starting at September 22 or so (the Autumn equinox), the sidereal clock would run faster than a 24 hour clock, gaining 4 minutes in the course of every 24 hour day. After 6 months, the sidereal clock would be 12 hours faster. After a year, the sidereal clock would be exactly a day faster: there are 366 sidereal days in a year.

I presume that astronomers like to use sidereal clocks because it helps them locate stars.

Do they also use sidereal watches? Is this a sidereal watch?zeitladen1.jpg

What about this clock?


I can’t decode the German text enough to find out.

Visually there seems to be no difference between the design of the 24 hour and sidereal dials. So you would be well advised to place one of these sidereal clocks next to an ordinary 24 hour clock, or else clearly label it as sidereal. As for watches, you could wear the sidereal watch on your right wrist, the ordinary 24 hour watch on the left…

I’ve had watches and clocks that seem to gain 4 minutes a day. Perhaps they were sidereal and I didn’t know it.

Zeitladen also sells radio-controlled sidereal clocks.

The Zeitladen site was interesting, particularly if your German was good!

The site is now closed, unfortunately.