French Republican 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:
Autumn:
Vendémiaire (from Latin vindemia, "vintage") Starting Sept 22, 23 or 24
Brumaire (from French brume, "mist") Starting Oct 22, 23 or 24
Frimaire (From French frimas, "frost") Starting Nov 21, 22 or 23
Winter:
Nivôse (from Latin Nivosus, "snowy") Starting Dec 21, 22 or 23
Pluviôse (from Latin pluviosus, "rainy") Starting Jan 20, 21 or 22
Ventôse (from Latin ventosus, "windy") Starting Feb 19, 20 or 21
Spring:
Germinal (from Latin germen, "seed") Starting Mar 20 or 21
Floréal (from Latin flor, "flower") Starting Apr 20 or 21
Prairial (from French prairie, "meadow") Starting May 20 or 21
Summer:
Messidor (from Latin messis, "harvest") Starting Jun 19 or 20
Thermidor (from Greek thermos, "hot") Starting Jul 19 or 20
Fructidor (from Latin fructus, "fruits") Starting Aug 18 or 19
Reference
Wikipedia: French Revolutionary Calendar
