The Mysteries of Time

How France adopted Greenwich Mean Time (and still fought back!)

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April 2024

How France adopted Greenwich Mean Time (and still fought back!)

Today, the Greenwich meridian rules supreme. But the international standardisation of time was the result of a scientific and diplomatic tug-of-war between the two great powers of Europe – England and France – that lasted almost a century.


here the captain fixed his position and used a chronometer to calculate his longitude, which he double-checked against his previous observations of hour angles. Then he told me: “Professor Aronnax, we’re in longitude 137 degrees 15’ west—” “West of which meridian?” I asked quickly, hoping the captain’s reply might give me a clue to his nationality. “Sir,” he answered me, “I have chronometers variously set to the meridians of Paris, Greenwich, and Washington, D.C. But in your honour, I’ll use the one for Paris.”

In this excerpt from 20,000 Leagues Under The Sea, Jules Verne reminds us of two 19th-century realities that we need no longer worry about: the existence of several concurrent prime meridians, and the crucial role of sailors, guardians of time, who were obliged to navigate between several complex geo-temporal systems.

Today, the Greenwich meridian rules supreme. But the international standardisation of time was the result of a scientific and diplomatic tug-of-war between the two great powers of Europe – England and France – that lasted almost a century. To understand how England won the battle, and imposed its own time zone, we have to go back to the 18th century, when advances made in modern horology made it possible to gradually abandon reliance on true solar time, which was read off sundials in the streets (you can read more about this in our article on the Palais Royal cannon clock on p. 112), in favour of local mean time, based on the trajectory of a fictional “average” sun.

In 1826, Paris became the first city to impose its own time on the entire country. Prior to that, countless different local times existed. From Marseille to Caen, everyone took their own sweet time! It was thanks to another mechanical invention – the train – that Paris time was adopted throughout the country. The railways required a single timetable to coordinate their routes, and they chose the capital as their reference.

This problem was not unique to France. In the United States, where the territory stretched across seven longitudes, and multiple companies shared the railroad network, standardising time was an early necessity. In 1876, a Canadian engineer named Sandford Fleming was the first to devise a system dividing the Earth up into 24 longitudinal time zones. Being originally from England, he naturally chose the Greenwich meridian, where the Royal Observatory was located, as the starting point for his system. His proposal was accepted at the General Time Convention, which took place on 11 October 1883 in Chicago.

A few days later, in Rome, a number of countries, including France, met to discuss this new system at the Conference of the International Geodesic Association. But the French delegation seemed ambivalent, and did a poor job of defending the Parisian meridian against Greenwich. There were rumours that the French had made a backroom deal with the English, according to which the Crown would agree to adopt the metric system in exchange for France’s support for the English meridian. Greenwich was approved by the French in a final vote, much to the embarrassment of Paris.

As the time of the 1884 International Prime Meridian Conference in Washington D.C., convened to define a standard universal time, approached, the English were in a strong position. Reluctant to let them win, the French delegation opted for the alternative strategy of proposing a neutral meridien – a universalist choice in the Enlightenment tradition. It could pass through the Bering Straits or the Azores, French astronomer Jules Janssen contended. But his arguments failed to convince and Greenwich was adopted as the prime meridian by 21 votes to one, with two abstentions.

Paris took umbrage and declined to adopt the new standard. In 1891 France abolished local time and adopted Paris time for the entire territory. In 1896, parliamentarian Gabriel Deville attempted to pass a law adopting the new international system based on Greenwich, but he omitted to mention the Paris meridian and the bill was rejected. The following year, Louis Boudenoot found a loophole. His amended text read: “The legal time in France and Algeria is the time, by Paris Mean Time, minus 9 minutes and 21 seconds,” which is the difference between Paris and Greenwich. By mentioning the French meridian by name, and by eliminating from the text all mention of “perfidious Albion”, the law passed without debate. National honour was preserved! Nevertheless, it wasn’t until 1911 that the text was fully adopted by France. For Paris to capitulate, it first had to find a way to place itself back in centre stage. The solution was… the Eiffel Tower! Struggling to come up with a reason to keep it after the Universal Exposition in Paris in 1889, Gustave Eiffel found unexpected salvation in the telegraph. With the help of the army, he installed an antenna so high that it was capable of sending a signal to the Algerian coast. Connected to the Paris Observatory, the Eiffel Tower antenna transmitted hourly time signals that enabled ships located thousands of miles away in every direction to set their clocks.

However, Paris was still 65 thousandths of a second adrift from Greenwich Mean Time, since the 9 minutes and 21 seconds specified in the law were not precise enough. The problem was resolved in 1978 by the adoption of Coordinated Universal Time (UTC), based on atomic time and the rotation of the Earth. It provided the opportunity for France to regain the upper hand once again. As historian Jacques Gapaillard explains, this new international time standard was developed at the International Bureau of Weights and Measures in Sèvres, on the Paris meridian!

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