French Republican (revolutionary) calendar

With all of the rapid developments in technology and the natural sciences throughout the 18th century, accurate measurements and calculations became necessary requirements for the design of any widely adopted calendar. It was during this time that the calendar ceased to be an exclusively ecclesiastical affair, and became of interest to everyone. A calendar system built on the arrangement of faith-based holidays and steeped in esoteric rules was no longer seen as suitable for a populace that increasingly viewed itself as secular and enlightened. The emergent industrial society demanded standardisation across the board, and this affected all systems of measurement, such as distance, weight, and time.

The predecessor to the French Republican calendar was a yearbook called the Almanac des Honnêtes gens (Almanac of the Honorable People) published in 1788 by Sylvain Maréchal (* 1750 - † 1803). The calendar months still had the usual number of days, but their order was changed, with the year beginning in March, and the months were given new names. The biggest change, however, was the removal of most of the saints. They were replaced with "venerable" people, such as scientists, artists, doctors, theologians, and statesmen. Even a few saints got to stay on the list, but so did the mistress of the king, a corsair. For this act, the author was given three months in a dungeon.

The Republican (often called Revolutionary) calendar is a product of passionate opposition to the old order during the Great French Revolution. The detachment from the old calendar was spontaneous and without training, so it should come as no surprise that it was also quite confusing. In the 1790s, it began to appear in official documents dated back to the Years of the Freedom (ère de la Liberté), systematically rejecting the idea of a Christian year. Unfortunately, the epoch was not clearly defined. Sometimes the epoch of the new era was considered to be on 14 July 1789, other times it was 1 January, and sometimes both in the same year. Finally, on 2 January 1792, the Legislative Assembly decided that the official documents would be dated to the Era of Freedom, with 1 January 1792 declared as the start of Year IV of Freedom. The year then returned to its original start date of 1 January, which had been originally introduced in the country as far back as 1564 (Édit de Roussillon). When the dating system was manipulated once again, this time to accommodate the years of Equality (l'an de l'Égalité), the start date was moved to 10 August. After the proclamation of the republic on 21 September 1792, the Convention decided that the era of the Republic (l'an de la République Française) would begin on this day, while the second year of the Republic would begin, once again, on 1 January 1793.

Finally, in December 1792, a commission was appointed to propose a new calendar, whose members were all part of the prestigious French Academy of Sciences:

After nine months of work by the commission, its chairman submitted a draft for a new calendar on 20 September 1793. The beginning of the era of the Republic was chosen as the day of the autumn equinox, which had occurred the previous year on 22 September 1792. The year was to have twelve months, each of an equal length of thirty days. In addition, each month was divided into thirds (10 days each). Since there were still five days left, they were appended to the end of the year as “additional days” (jours complémentaires). Any leap day that needed to be added was inserted among these days as a sixth additional day. Astronomical calculations determined when it would be inserted, so the calendar could be harmonious with nature. This would normally take case every four years, but sometimes it would appear every five years. The new calendar was enacted by law on 5 October 1793 (14. Vendémiaire l'an II). The Commission also proposed names for individual months and days of decades, but the Convention rejected these proposals, because this proved impractical. For example, imagine trying to internalise a term that conveys the 5th day of the 2nd decade of the 3rd month of the 2nd year without feeling more disoriented than helped. So, another commission was appointed to create new names for the months and days. The members of this commission were:

This commission submitted a proposal for the names of months and days on 24 October 1793. This proposal was enacted on the 4th Frimaire l'an II (i.e. 24 November 1793). Each year was set to begin at midnight on the day of the autumn equinox according to the true solar time of the Paris Observatory. Furthermore, the names of the months were created so that the months of each quarter had a consistent ending. Fabre d'Églantine justified it as follows:

We tried to use the imitation of the natural sounds of language in the composition and prosody of these words and in the mechanism of their endings, so that the names of the months forming autumn have a serious sound and medium pace, the names of winter sounds carry a heavy sound and a slower pace, the names of spring sound cheerful and are short paced, while the names of summer carry a resonant sound with a wide pace.
Thus, the first three months of the year which form autumn, have in their etymology, the first harvest for the vintners, and take place from September to October; this month is called vendémiaire; the second month is named in accordance with the gloomy and low mists, and, so to speak, the sweating of nature from October to November; this month is named brumaire; the third month is named in accordance with the wet or dry cold felt from November to December; this month is called frimaire.
The three winter months have meaning imbued in their etymology as well, with the first named according to the snow that whitewashes the earth from December to January, this month is called nivôse; the second, due to the rains, which are generally more abundant from January to February, is called pluviôse; The third, due to the showers that pour down and the wind that dries the earth from February to March, is called ventôse.
The three months of spring have meaning imbued in their etymology likewise, with the first in accordance to the leaven and development of the sap from March to April; this month is called germinal; the second, because of to the budding flowers from April to May, this month is called floréal; The third is named according to the abundant fertility and the harvest on the meadows from May to June; this month is called the prairial.
The three months of the summer have their names rooted in their etymology, with the first according to the appearance of the undulating landscapes and the golden harvest that covers the fields from June to July; this month is called messidor; the second, according to the heat of both the sun and the earth, which fills the air from July to August, is called thermidor (we thought at one point to name it fervidor [month of heat]); The third, according to the fruit that turns golden and ripens in the sun from August to September, is called fructidor.
Names of months of the year
1stVendémiaireWine Harvesting
8thFloréalFlower, Bloom
9thPrairialPrairie, Meadow

Each month was to have thirty days, and each month was divided into thirds (dècadi). Of the ten days, nine were working days, with the tenth day set aside for rest:

Names of the days in each third of the month

All of the dècadi (tenths), new years, and sabbaths, were set aside for feasting:

Names of the holidays in the months
Vendémiaire1La Proclamation de la RépubliqueDeclaration of the Republic
10La NatureNature
20Le Genre HumainThe Human Genus
30Le Peuple FrancaisThe French People
Brumaire10Les Bienfaiteurs de l'HumanitéThe Benefactors of Humanity
20Les Martyrs de la LibertéThe Martyrs of Liberty
30La Liberté et l'EgalitéLiberty and Equality
Frimaire10La RépubliqueThe Republic
20La Liberté du MondeFreedom of the World
30L'Amour de la PatrieLove of the Fatherland
Nivôse10La Haîne des Tyrans et des TraîtersHatred of Tyrants and Traitors
20La VeritéTruth
30La JusticeJustice
Pluviôse10La PudeurModesty
Ventôse10La FrugalitéFrugality
20Le CourageCourage
30La Bonne FoiGood Faith
20Le DésintéressementSelflessness
30Le StoicismeStoicism
20La Foi ConjugalConjugal Faith
30L'amour PaternelPaternal Love
Prairial10La Tendresse MaternelleMaternal Tenderness
20La Piété FilialeFilial Piety
Messidor10La JeunesseYouth
20La VirilitéVirility
30La VieilleseThe Aged
Thermidor10Le MalheurMisfortune
Fructidor10Nos AieuxOur Ancestors
20La PostéritéPosterity
30Le BonheurHappiness
Jours complémentaires
(Additional Days)
1Jour de la VertuDay of Virtue
2Jour du GénieDay of Genius
3Jour du TravailLabor Day
4Jour de l'OpinionOpinion Day
5Jour des RécompensesAward Day
6Jour de la RévolutionDay of the Revolution

In addition, every day of the year still had its own name. The author explains it as follows:

We arranged the names of the real treasures of rural farming in order, according to month, and separated into columns. Grains, spices, flowers, fruits, and vegetation were distributed so that the place and date of each fruit occupies the time and day when nature gives it to us. Each dècadi (tenth day) is marked with the name of a field tool used for agriculture, at the time it is to be used, so that on the day of rest the farmer finds in the calendar a consecrated tool to be used in his hand the next day... this method will instill in all French citizens, from the earliest age, an inability to be ignorant of the unseen toil that constitutes the alphabet of rural farming.

The additional days at the end of the year were collectively called sans-culottides, but were soon renamed jours complémentaires. Of course, each additional day also had its own name (e.g. the leap day itself was called Jour de la Révolution, or in English, Day of the Revolution).

The years were written in Roman numerals in the French Republican calendar, which is quite confusing in the case of higher numbers. The individual changes in the Republican calendar described above can then be summarised in the table below:

15 July 178931 December 1789Year I of Freedom
1 January 179031 December 1790Year II of Freedom
10 August 179221 September 1792Year I of Equality
22 September 179231 December 1792Year I of the Republic
1 January 179321 September 1793First Year II of the Republic, then Year I of the Republic
22 September 179324 November 1793New names for the days and months
22 September 179321 September 1794Year II of the Republic
22 September 180531 December 1805Last XIV year of the Republic

In addition to changes in the calendar, the French Revolution also brought about changes in the counting of time. The day was divided into ten hours, with the hour set at one hundred minutes and each minute set at one hundred seconds. This change brought about immediate confusion and was soon after withdrawn. There were also a number of other problems with the new calendar which led to complaints. For example, the extra days tagged onto the end of the year fell right in the middle of harvest work and threw people off their typical rhythm. The new names themselves, for the days and months of the year, were generally disliked by the public. Then there was the abolition of the traditional seven-day week in lieu of a ten-day week, which brought about the most pushback and complaint. While France experimented with all of these new ways to measure time, they did it alone; no one would ever adopt their system. Finally, by decree of the 22nd Fructidor l'an XIII (9 September 1805), France returned to the Gregorian calendar. The last day of the republican calendar was the 10th Nivôse l'an XIV, with the following day being 1 January 1806.

A brief revival of the French Republican calendar took place during the Paris Commune in 1871. The Republican date was used on 6 May 1871 (16th Floréal LXXIX) in the French Republic's Officiel de la République française. With the end of the Paris Commune on 28 May 1871, France switched back to the Gregorian calendar, thus marking a definitive end to the usage of the republican calendar.

It should be noted that the names of the months from the republican calendar continue to live on in the French Navy. During the WWI, submarines bore the names of individual months, with an entire class of submarines named after the first launched submarine they ever launched: Pluviôse. And even today, frigates take the names of some months, such as the Floréal class.

The problem with leap years

Unfortunately, the decree of the National Convention contained an unintended contradiction for the insertion of the leap day. Point Ⅲ. states:

Each year begins at midnight, on the day when the autumnal equinox occurs, according to the true solar time of the Paris Observatory.

But then point Ⅹ. says:

The period of four years, at the end of which it is usually necessary to add an extra day, is called the franciade.

According to the rule for the autumn equinox, it was typically necessary to insert a leap day after four years, but sometimes after five, and since the intervals between these leap years are irregular, they cannot be easily calculated. They depend on accurate and complex astronomical calculations.

Gilbert Romme tried to eliminate this irregularity by using rules similar to the Gregorian calendar. Every fourth year would have a leap year, except for centuries ending in 00 (the so-called “centenary years”); these years would only be leap years if they were divisible by 400. After increasing the accuracy this way, he added yet another rule that years divisible by 4000 will not be leap years. The average length of a year in the French Republican calendar would then be:

365 + 1/4 - 1/100 + 1/400 - 1/4000 = 365.24225 days

This mistake of one day would only become apparent in about 17,000 years, but the rule was never enforced. Unfortunately for Romme, like many other intellectuals of his time from wealthy families, he was sentenced to death; he would soon commit suicide to avoid a public execution. His correction never adopted, the leap years carried on as follows: 3, 7, and 11. The next year would’ve been 15, but in the meantime, the French Republican calendar ended up getting abolished. According to the astronomical rule, another leap year was supposed to follow in another five years, at year 20. Romme's rule seems to have been intended to take year 20 as its base, this choice most likely driven by the fact that dividing by four is easily recognisable, as it was used in the Christian era. On the page What is today according to the French Republican calendar, you will find out what day it would be according to this calendar, using both rules. Most converters between calendars on the Internet prefer Romme's (invalid) leap year rule, simply because it’s an easy calculation to perform. Its implementation is trivial in its simplicity, as opposed to the more complicated (and accurate) astronomical determination of a leap year.

As mentioned above, the French themselves were confused by all of this. Proof of this is the calendar of Manuel pour la concordance des Calendriers, editions from 1806 and 1822, where the following leap years were also recorded. The picture on the left shows a calendar from 1806, where it is written that the next leap years (anées sextiles) will be 15, 20, 24, and 28 (in the original written in Roman numerals). Here they count both the astronomical rule for leap years according to point Ⅲ’s decree, and with Romme's rule starting only from the year 20. On the right is the calendar from 1822, where for it differs by stating that the leap years should be 15, 19, 23, 27, and 31. Here they seem to prefer the leap year, regularly, every four years, according to point Ⅹ of the Decree of the Convention. This means that the accuracy of the French Republican calendar would have been of lower quality than the Gregorian calendar, but similar to the Julian calendar. Any improvements it claimed to make were simply a wash. Even the reintroduction of the republican calendar in the times of the Paris Commune failed to shed light on the chosen rule of inserting leap years, as both systems gave the same calendar dates for 1871.