dating system that was adopted in 1793 during the French Revolution and which was intended to replace the Gregorian calendar with a more scientific and rational system that would avoid Christian associations. The Revolutionary Convention established the calendar on October 5, 1793, setting its beginning (1 Vendémiaire, year I) to a date nearly a year prior (September 22, 1792), when the National Convention had proclaimed France a republic.

The French republican calendar was based on a secular calendar first presented by Pierre-Sylvain Maréchal (Maréchal, Pierre-Sylvain) in 1788. The 12 months of the calendar each contained three décades (instead of weeks) of 10 days each; at the end of the year were grouped five (six in leap years) supplementary days. The months in order—beginning with one corresponding to the Gregorian months of September and October—were Vendémiaire (meaning “vintage”), Brumaire (“mist”), Frimaire (“frost”), Nivôse (“snow”), Pluviôse (“rain”), Ventôse (“wind”), Germinal (“seedtime”), Floréal (“blossom”), Prairial (“meadow”), Messidor (“harvest”), Thermidor (“heat”), and Fructidor (“fruits”). The names were the invention of poet Philippe Fabre d'Églantine (Fabre d'Églantine, Philippe). Each of the 360 days in the year was named for a seed, tree, flower, fruit, animal, or tool, replacing the saints'-day names and Christian festivals.

Among the notable historical events marked by the republican calendar were the consolidation of the Revolutionary government on 14 Frimaire, year II (December 4, 1793), legislation that accelerated the Reign of Terror on 22 Prairial, year II (June 10, 1794), the arrest of Robespierre and the Thermidor Reaction on 9 Thermidor, year II (July 27, 1794), the insurrection of the sansculottes on 1 Prairial, year III (May 20, 1795), and the various coups d'état that marked the ascendancy of the Directory and then of Napoleon on 18 Fructidor, year V (September 4, 1797), 30 Prairial, year VII (June 18, 1799), and 18 Brumaire, year VIII (November 9, 1799).

The Gregorian calendar was reestablished in France when the republican calendar was abandoned by the Napoleonic regime on January 1, 1806.