Click on this clock to display today's date on French Revolutionary Calendar .


There's no doubt about. The Frech Revolutionary Calendar was far more useful and efficient than our conventional calendar. But also there's no doubt that if a calendar is used by one only nation in the world, it will soon dissapear, because of the impossibilty to coordinate dates and to schedule events with the international trade of other countries. However, this calendar was in use for 12 years. From 1793 to 1806, when it was abolished by Napoleon.


Revolutionaries had a passion for the construction of a new world more practice and more functional than that which was inherited from the Old Regime. And they were focused on the decimal system for that purpose, for all measures, of weight, space and, why not, also for time lenghts. After all, they were right: it's easier to calculate in a decimal system (adding or substracting zeros) than in a, for example, duodecimal system. The clock in the image above, is a dual clock, displaying the time in both the Revolutionary decimal time and in the conventional 12 hours time. They set a time system based in 10 hours a day: the zero hour was the midnight and the noon the 5th hour. These hours were divided in 100 minutes, and every minute in 100 seconds. In consequence, to complete a solar day, with 100.000 seconds equivalents to our regular 86.400 seconds per day, the Revolution time seconds must have been shorter. A Republican second was 0,864 of our conventional second. A decimal minute was 1 minute 26 seconds of our time. And a decimal hour, 2 hours 24 minutes. The system wasn't bad, but nobody felt comfortable with it. And it lasted only 6 months; it was abolished the same day than the metric decimal system was implemented. For the lenght, volume and weight measures, the revolutionaries certainly solutioned much of the heavy weight that the French were bearing from centuries. Our arithmetic is utterly based on the decimal system; when we write "123", for instance, 3 is a unit, 2 are 2 groups of ten, and 1 is a hundred. We multiply by 10 to the left, and at contrary, we divide by 10 to the right side. That's why it's easy to say that 14 Kilometers are 14,000 meters. But to calculate how many inches are 5 yards, 2 feet and 8 inches is, no doubt, a headache. Likewise, when we divide between 4 people 1,2 kg. of rice, it's fast to realize that it's 1200 grames and corresponds 300 grames for each one of them. But to share between 4 people 7 pounds and 8 ounces, considering that every pound is 16 ounces, is not that easy. To make calculations in the routinary life, complex additions and substractions were needed, not the simple ones, which left the population, mainly illeterate, far from the commercial activity. Until this point, a bravo for the Revolutionaries. They simplified a complex world, leaving it at the reach of everyone.

But, all that passion for being functional and for the decimal numeral system was not the only reason they had to change the conventional calendar. They were specially focused about remove all vestiges of religious culture, and, as everybody knows, our Gregorian Calendar was made by a Pope, with every day of the year dedicated to saints. Moreover, Gregorian Calendar is irregular and whimsical in many aspects, divided in 12 months of different lenght, months of 30 and 31 days each and one of 28 or 29; weeks do not match in an exact number with months. Our calendar is coming from an old evolution and was adapted from a primitive lunar calendar, to a lunar-solar calendar, and finally to a solar-tropical calendar, adjusting days every some years to match with the astronomic reality. Its division in months is obviously whimsical; initially they were only 10 months, from March to December, and later January and February were added; but February, being a bad luck month for the Romans, was made shorter.

Well, revolutionaries got a solution for all of that: they made a solar calendar, beginning on the Autumn equinox observed from Paris, (an equinox is that moment in the year when the center of the Sun is in the same plane as the Earths' equator, and the day has the same lenght than the night; it happens twice a year), on September 22nd, with 12 months of 30 days each: 360 days. To reach the 365 of the solar year, they added 5 days at the end of the year. And in order to adjust leap years, given that a solar year is 365 days and a 1/4, every 4 years they made those hollidays 6, instead of 5.


In September 1792 France was governed by the National Convention, with Georges Jacques Danton as MInister of Justice. On September 21st 1792 the monarchy was abolished and the First Republic was proclamed. In January 1793 the king Louis XVI was executed by the guillotine. And, in October 16th 1793, the same day the queen Marie-Antoinette was also beheaded by execution, revolutionaries were specially focused in two important projects: the creation of a new Civil Code, only one for the whole nation, and a new calendar.

Long sessions and debates were followed about the calendar, with mathematicians, astronomers, poets and a painter, Jacques Louis David. They had the intervention of a mathematician and geometrist, Gaspard Monge, who was simoultaneously Minister of Marine, and Charles Romme, mathematician, the brother of Charles-Gilbert Romme, a montagnard representative for the department of Puy-de-Dôme, who was the chief of the project. The names of days and months were designed by the poets, based in elements of the Nature. The poet Philippe Fabre d'Eglantine, representative at the Convention for the Department of the Seine and Danton's Secretary at the Ministry of Justice,was one of the main propulsors of the project. Also was there André Chénier, son of a Louis XVI's diplomatician, and brother of Joseph-Marie Chénier, (the author of the Chant du Départ, called the Second Marselleise, which was the Anthem of the Napoleon Empire). The painter Jacques Louis David, conventional representative at that time, was in charge to rule the Revolution's hollydays.

On September 20 1793, after being the project approved by the Commision, Romme introduces it before a National Convention session, and it was approved. October 5th is voted a Convention's decree, by which the Calendar starts to be in force, and on October 24th the decree is re-confirmed, being added the days and months.

This calendar had a retroactive effect: the first day of the year's calendar was that one of the former year: September 22nd 1792, was the first day of the Republic.

This calendar was very useful , but what the revolutionaries made hard to understand was the name of the years with roman numerals. Even though for that time (and for the 20% of population who read) roman numerals were for them more familiar than for us today.

The Calendar, then, was ruled this way :

-A year of 12 months , starting on September 22nd and ending on September 21st.:


Therefore, the year starts on the first day of Vendémiaire every year. The months, as you can see, rhyme between them, which probably was an idea of the poet Fabre d'Églantine. It's make them easier to remember.

-The months, were divided not in 7 days weeks (irregulars) but into regular periods of 10 días each, being called, instead of "weeks", "decades".

-The days of a decade (instead of Monday, Tuesday, etc.) were called this way:

-Primidi (first day), Duodi, (2nd day), Tridi, (3rd day), Quartidi (4th day), Quintidi (5th day), Sextidi (6th day), Septidi (7th day), Octidi (8th day), -Nonidi (9th day), Décadi (10th day).

Pretty evident and very easy to remember .




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