From a post of 24 October 2009 by J.K. Baltzersen.
So much foolishness and work was put into this calendar...
The Republican calendar year began at the autumn equinox and had twelve months of 30 days each, which were given new names based on nature, principally having to do with the prevailing weather in and around Paris:
Vendémiaire (from Latin vindemia, "grape harvest") Starting 22, 23 or 24 September
Brumaire (from French brume, "fog") Starting 22, 23 or 24 October
Frimaire (From French frimas, "frost") Starting 21, 22 or 23 November
Nivôse (from Latin nivosus, "snowy") Starting 21, 22 or 23 December
Pluviôse (from Latin pluvius, "rainy") Starting 20, 21 or 22 January
Ventôse (from Latin ventosus, "windy") Starting 19, 20 or 21 February
Germinal (from Latin germen, "germination") Starting 20 or 21 March
Floréal (from Latin flos, "flower") Starting 20 or 21 April
Prairial (from French prairie, "pasture") Starting 20 or 21 May
Messidor (from Latin messis, "harvest") Starting 19 or 20 June
Thermidor (from Greek thermon, "summer heat")Starting 19 or 20 July
Fructidor (from Latin fructus, "fruit") Starting 18 or 19 August
The month is divided into three décades or 'weeks' of ten days each, named simply:
primidi (first day)
duodi (second day)
tridi (third day)
quartidi (fourth day)
quintidi (fifth day)
sextidi (sixth day)
septidi (seventh day)
octidi (eighth day)
nonidi (ninth day)
décadi (tenth day)
Instead of most days having an associated saint as in the Roman Catholic calendar of saints, each day has an animal (days ending in 5), a tool (days ending in 0) or else a plant or mineral (all other days).
The Concordat of 1801 re-established the Roman Catholic Church in France with effect from Easter Sunday, 18 April 1802, restoring the names of the days of the week with the ones they had in the Gregorian Calendar, while keeping the rest of the Republican Calendar, and fixing Sunday as the official day of rest and religious celebration.
Napoléon finally abolished the calendar with effect from 1 January 1806 (the day after 10 Nivôse an XIV), a little over twelve years after its introduction. However, it was used again during the brief Paris Commune, 6–23 May 1871 (16 Floréal–3 Prairial An LXXIX).
Writen on this, 7th (Septidi) of Brumaire, of AN 218.
St Marie-Antoinette Queen martyr,
pray for us...
Dieu le Roy!