The French Revolutionary Calendar

From the beginning of the French Revolution (14 July 1789) the years of freedom were counted, mostly alongside the Gregorian year. On 22 September 1792, this era was replaced by the years of the republic, the first of which was the Gregorian year 1792. The second year of the republic was begun on 1 January 1793. But, the radical change in the French state was to be expressed by means of a new calendar, which led to the elaboration of a new calendar wholly independent of the Gregorian calendar.

On 5 October 1793, the French government decided to introduce the Revolutionary calendar. The era of this calendar was 22 September 1792, Gregorian. In France, a decimal system of units was created, and time should be measured in decimal units, too. Therefore, a year was divided into twelve months of three decades each. The remaining 5 or, in leap years 6 days, called jours complémentaires and declared feast days, were being placed at the end of the year. Days and months simply were to be numbered, which would have led to days like "the seventh day of the first month of the fifth year of the republic".

There was no fixed leap year pattern, but the year was begun with the day of the autumnal equinox, which was determined by observation at the location Paris. The period from one leap year to the succeeding leap year was called franciade.

Before putting the calendar in effect, a commission was given the task of checking it. The numbering of days and months was criticized, and the poet Fabre d'Eglantine created poetic names for the months according to the season in which they occur.

No.	Name	Meaning
1	Vendémiaire	vintage month
2	Brumaire	fog month
3	Frimaire	sleet month
4	Nivôse	snow month
5	Pluviôse	rain month
6	Ventôse	wind month
7	Germinal	seed month
8	Floréal	blossom month
9	Prairial	pasture month
10	Messidor	harvest month
11	Thermidor	heat month
12	Fructidor	fruit month
13	Sansculottides	additional days

	No.		Name
	1		primidi
	2		duodi
	3		tridi
	4		quartidi
	5		quintidi
	6		sextidi
	7		septidi
	8		octidi
	9		nonidi
	10		décadi

Day	Name	Meaning
1	jour de la vertu	virtue day
2	jour du génie	genius day
3	jour du labour	labour day
4	jour de la raison	reason day
5	jour de la recompense	reward day
6	jour de la révolution	revolution day

Fabre d'Eglantine even gave a name to every single day of the year, designating the décadi and quintidi with names of agricultural tools and animals, respectively. The remaining days were called after trees, bushes and plants.

On 24 November 1793 the calendar went into effect with the Fabre d'Eglantine names. Only two years later, in August 1795, the Sansculottides were named "jours complémentaires" again, while Fabre d'Eglantine had been executed on 16 Germinal II. Writing dates with the number of the day and the decade was not commonly adopted, too.

The lack of a regular leap year pattern made it impossible to date future events unless they were to occur in the current year. So Gilbert Romme proposed a leap year rule similar to that of the Gregorian calendar. This rule said, that every 4th year should have been a leap year, except every 100th, which was to be a common year, except of every 400th year, which should stay a leap year, except every 4000th year, which again should be a common year. But, before this rule could be adopted a proposal was brought forward in the Senate on 2 September 1805 suggesting the abolition of the Republican calendar and the return to the Gregorian calendar. This was approved of later, and the Gregorian calendar re-adopted on 1 January 1806. Therefore, the last day the French Revolutionary calendar was in effect was 10 Nivôse XIV, or 31 December 1805.