French Revolutionary calendar, the official calendar of France, Nov. 24, 1793–Dec. 31, 1805. Its introduction was decreed by the Convention on Oct. 5, 1793, but it was computed from Sept. 22, 1792, the autumnal equinox and the day after the proclamation of the republic. Supposedly philosophical and mathematical in its basis, it was divided into 12 months of 30 days (their names were invented by Fabre d'Églantine): Vendémiaire (vintage month); Brumaire (fog); Frimaire (sleet); Nivôse (snow); Pluviôse (rain); Ventôse (wind); Germinal (seed); Floréal (blossom); Prairial (pasture); Messidor (harvest); Thermidor (heat); Fructidor (fruit). The remaining five days, called sans-culottides, were feast days; they were named for Virtue, Genius, Labor, Reason, and Rewards, respectively. In leap years (the years III , VII , and XI ) the extra day, the last of the year, was Revolution Day. The first day of the year (1 Vendémiaire) of year I , II , III , V , VI , and VII fell on Sept. 22 of the corresponding year A.D.; in the years IV , VIII , IX , X , XI , XIII , and XIV , it fell on Sept. 23; in the year XII , it fell on Sept. 24. There was no week; each month was divided into three decades of ten days each, with every 10th day ( décadi ) a day of rest. For the outstanding events known by the names of the revolutionary months in which they occurred, see Vendémiaire; Brumaire; Thermidor; Fructidor.