The Republican calendar year began the day the autumnal equinox occurred in Paris, 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. The extra five or six days in the year were not given a month designation, but considered Sansculottides or Complementary Days.
Autumn:
Vendémiaire (from French vendange, derived from Latin vindemia, "vintage"), starting 22, 23, or 24 September
Brumaire (from French brume, "mist"), starting 22, 23, or 24 October
Frimaire (From French frimas, "frost"), starting 21, 22, or 23 November
Winter:
Nivôse (from Latin nivosus, "snowy"), starting 21, 22, or 23 December
Pluviôse (from French pluvieux, derived from Latin pluvius, "rainy"), starting 20, 21, or 22 January
Ventôse (from French venteux, derived from Latin ventosus, "windy"), starting 19, 20, or 21 February
Spring:
Germinal (from French germination), starting 20 or 21 March
Floréal (from French fleur, derived from Latin flos, "flower"), starting 20 or 21 April
Prairial (from French prairie, "meadow"), starting 20 or 21 May
Summer:
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
Sansculottides (Complmentary Days)
Five extra days – six in leap years – were national holidays at the end of every year. These were originally known as les sans-culottides (after sans-culottes), but after year III (1795) as les jours complémentaires:
1st complementary day: La Fête de la Vertu, "Celebration of Virtue", on 17 or 18 September
2nd complementary day: La Fête du Génie, "Celebration of Talent", on 18 or 19 September
3rd complementary day: La Fête du Travail, "Celebration of Labour", on 19 or 20 September
4th complementary day: La Fête de l'Opinion, "Celebration of Convictions", on 20 or 21 September
5th complementary day: La Fête des Récompenses, "Celebration of Honors (Awards)", on 21 or 22 September
6th complementary day: La Fête de la Révolution, "Celebration of the Revolution", on 22 or 23 September (on leap years only)
The French Republican Calendar calendar is a calendar that consists of (in addition to the 100-second minutes, 100-minute hours and 10 hour days) 10-day weeks, 30-day months, and 12-month years.
The year consists of 12 30-day months, with an extra 5-6 days left over. These are reserved for celebrational holidays.
The tenth day, décadi, replaced Sunday as the day of rest and festivity.
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)
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Metric Time
This method of date tracking is associated with Metric Time.