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Finding a date in the archives can be a real puzzle! Discover the specifics of the Gregorian and French Republican calendars and learn how to easily convert them for your French genealogy research.
©Gallica - BnF
When delving into the archives to trace the history of your ancestors, the question of dates can quickly become a puzzle. France has indeed experienced several dating systems, and it is not uncommon to encounter registers using a calendar unfamiliar to us. Two systems stand out in particular: the Gregorian calendar, which we still use today, and the Republican calendar, established during the French Revolution. To avoid errors and correctly interpret these records, it is essential to understand what these calendars represent and how to convert them.
The Gregorian calendar was established by Pope Gregory XIII in 1582 to correct the drift of the Julian calendar, which had been in use since antiquity. It introduced a new rule for leap years and removed 10 days in October 1582 to realign the civil year with the solar year.
However, its adoption was not immediate in France. Although the Papal States, Spain, and Portugal adopted it in 1582, France did not implement it until 1583. Some countries, such as Great Britain, did not adopt it until the 18th century. For genealogists, it is therefore crucial to consider this transition when reading period documents.
Before 1583 in France: beware of dates in the Julian calendar.
Check the registers of other countries that may have a different adoption timeline.
Be cautious of transcription errors in the archives, especially for end-of-year records (where the transition from one year to the next could differ depending on the systems in use).
Established by the National Convention in 1793, the Republican calendar aimed to break with the Ancien Régime and establish a more rational system, distancing itself from the religious references of the Gregorian calendar.
It began on September 22, 1792, the date of the proclamation of the First Republic, and introduced a division into 12 months of 30 days, themselves divided into decades of 10 days (replacing the 7-day week). Each day of the decade had a specific name (Primidi, Duodi, Tridi, etc.), and Sundays were abolished.
At the end of the year, 5 days (or 6 in a leap year) called complementary days or Sans-culottides were added to reach a total of 365 or 366 days.
The names of the months were created by the poet Fabre d'Églantine, inspired by the seasons and natural phenomena. They are divided into four seasons of three months each:
Vendémiaire (from Latin "vindemia" = harvest) → September 22 - October 21 → Month of the grape harvest
Brumaire (from "brume" = mist) → October 22 - November 20 → Month of fog
Frimaire (from "frimas" = frost) → November 21 - December 20 → Month of first frosts
Nivôse (from "nive" = snow) → December 21 - January 19 → Month of snow
Pluviôse (from "pluvia" = rain) → January 20 - February 18 → Month of rain
Ventôse (from "ventus" = wind) → February 19 - March 20 → Month of winds
Germinal (from "germen" = germ) → March 21 - April 19 → Month of germination
Floréal (from "flor" = flower) → April 20 - May 19 → Month of flowering
Prairial (from "prairie") → May 20 - June 18 → Month of meadows
Messidor (from "messis" = harvest) → June 19 - July 18 → Month of harvests
Thermidor (from "thermos" = heat) → July 19 - August 17 → Month of heat
Fructidor (from "fructus" = fruit) → August 18 - September 16 → Month of fruits
These additional days allowed the calendar to align with the solar year and also served to celebrate the Republic and its values:
Day of Virtue (September 17)
Day of Genius (September 18)
Day of Labor (September 19)
Day of Opinion (September 20)
Day of Rewards (September 21)
Day of the Revolution (September 22, added in leap years)
Although the idea of a Republican calendar based on nature and reason was innovative, its use quickly showed limitations:
The decade of 10 days was poorly accepted by the population, especially by workers who lost a day of rest every seven days.
Conversions between the Republican calendar and the Gregorian calendar were complex and posed administrative problems.
Napoleon I, concerned with stabilizing the country, reinstated the Gregorian calendar on January 1, 1806.
It saw only a brief return in 1871, during the Paris Commune, but was never reused sustainably.
Since civil status records from 1793 to 1805 are often written only in the Republican calendar, it is essential to know how to convert these dates. Fortunately, tools exist to help us!
On Geneafinder, the Republican date converter included in the entry of your genealogical tree allows you to obtain the Gregorian equivalent with a single click. A valuable time-saver for precisely identifying the birth, marriage, or death of an ancestor during this revolutionary period.
