Dating system adopted in 1793 during the French Revolution .
It sought to replace the Gregorian calendar with a scientific and rational system that avoided Christian associations. The 12 months each contained three décades (instead of weeks) of 10 days each, and the year ended with five (six in leap years) supplementary days. The year began with the autumnal equinox and the day on which the National Convention had proclaimed France a republic, 1 Vendémiaire, Year I (Sept. 22, 1792). The other autumn months were named Brumaire and Frimaire; they were followed by the winter months Nivôse, Pluviôse, and Ventôse, the spring months Germinal, Floréal, and Prairial, and the summer months Messidor, Thermidor, and Fructidor. (All the names were derived from words for natural phenomena.) On Jan. 1, 1806, the Gregorian calendar was reestablished by the Napoleonic regime.