The 13-year revolutionary calendar

The French revolutionary (or republican) calendar was officially adopted in France on 24 October 1793. Its purpose was to replace the Gregorian calendar with a scientific and rational system that avoided Christian associations.

The calendar was created by a political commission with the help of a host of notaries, who included mathematicians, chemists, astronomers, a poet, a painter and the gardener at the Jardin des Plantes in Paris.

The new calendar was presented to the National Convention on 5 October 1793, but was computed from 22 September 1792, the autumnal equinox and the day after the proclamation of France as a republic.

The mathematicians contributed equal division of the months, with decimalisation of the measurement of time. The poets contributed the names of the days, with each day of the year given a specific name, chosen from the names of flowers, trees, plants, animals and farm tools.

The names of the months rhymed three by three, according to the “sonority” of the seasons, and the names given were supposedly characteristic for the time of year. For example, the month that includes the end of October was called Brumaire, from the French brume, meaning fog.

The 12 months each contained 30 days and were divided not into seven-day weeks but into “decades” of 10 days each. The last day in each decade replaced Sunday as a day of rest.

The remaining five days (six in a leap year), called “sans cullotides”, after the working class movement of the revolution, were feast days, and added on to the end of the year, in order to approximate the solar year. In leap years the extra day, the last in the year, was Revolution Day.

Aware of the unwieldy nature of a calendar whose first day of the year (the irregular autumn equinox) was never the same date, and in an attempt to detach his newly founded empire from the revolution and set it within the context of French history back to Charlemagne, Napoleon I abolished the calendar by imperial decree on 9 September 1805 and France resumed use of the Gregorian calendar on 1 January 1806.

The Republican calendar had lasted for just 13 years. It was, however, to have a brief revival during the Paris Commune, from 6 to 23 May 1871.