On September 22, 1792, the National Convention decreed that all public acts would be dated from the Year One of the French Republic. The monarchy had been abolished the day before, at about four in the afternoon, and the Convention, which had been debating what number to give the new era, settled on the day after as the first. France had been a kingdom by inheritance for about 1,300 years.
The calendar followed in October. It was the most thorough attempt of the revolution to remake how people counted. The Convention appointed a commission including the mathematician Gilbert Rome and the poet Fabre d'Eglantine, and it produced a calendar of twelve months of thirty days, with five or six leftover days at the end as the sans-culottides. Each month was thirty days, divided into three decades of ten, with the tenth day the day of rest. The months were named for their weather and their work: Vendemiaire for the grape harvest, Brumaire for the mist, Frimaire for the frost, Thermidor for the heat.
The motive was not only to get rid of the saints. A ten-day week meant no Sunday, which was the point as far as the dechristianisers were concerned, and it meant one day off in ten instead of one in seven. The days were named for agricultural tools and animals, so that 22 Vendemiaire was the day of the pear. The clock was decimalised at the same time: ten hours to the day, 100 minutes to the hour, It was abandoned within eighteen months. Nobody would use it.
Resistance was general. The church kept the sabbath, the countryside kept the fairs and the market days, and the government's own officials mostly carried both calendars. The Convention itself abolished the revolutionary calendar's religious basis in 1793 and then reimposed it. Thermidor and Brumaire became the names of the coups that ended the Terror and the Directory, which is the main reason anyone remembers them.
Napoleon restored the Gregorian calendar from January 1, 1806, about eighteen months after making himself emperor, and the Concordat of 1801 had already brought Sunday back. The Paris Commune briefly revived the revolutionary calendar in 1871, in its 79th year. The Republic that began on September 22 lasted, on paper, until 1804, and France has been a republic, on and off, ever since.