How to use the french republican calendar converter
- Choose a direction: Gregorian to Republican or Republican to Gregorian.
- For a Gregorian date, pick a date from 22 September 1792 to 31 December 1805. For a Republican date, enter the year as a number from 1 to 14, choose the month and enter the day.
- Read the converted date with its day name, the decade and the day of the year.
- Check the table for the date on which that Republican year began.
Formula
Day of the year = days since the start of that Republican year
Month = day of the year divided by 30, rounded up (months 1 to 12)
Days 361 to 365 or 366 are the extra days (month 13)
Decade day = (day of month - 1) mod 10 + 1
The year start dates for Years I to XIV are 22 Sep 1792, 22 Sep 1793, 22 Sep 1794, 23 Sep 1795, 22 Sep 1796, 22 Sep 1797, 22 Sep 1798, 23 Sep 1799, 23 Sep 1800, 23 Sep 1801, 23 Sep 1802, 24 Sep 1803, 23 Sep 1804 and 23 Sep 1805.
The coup of 18 Brumaire
Napoleon's coup took place on 9 November 1799. Year VIII began on 23 September 1799, which makes 9 November day 48 of the year. Day 48 is day 18 of month 2, Brumaire, so the date is 18 Brumaire VIII, an Octidi.
Another well-known date, 27 July 1794, falls on 9 Thermidor II, the day Robespierre fell. The extra days at the end of Year III included a sixth day, called the Day of the Revolution, on 22 September 1795.
How the calendar worked
The French Republican calendar replaced the Gregorian calendar in France from late 1793 and was dated back to 22 September 1792, the day the Republic was proclaimed. It had 12 months of 30 days, each split into three ten-day weeks called decades, with day names from Primidi to Decadi. Five extra days at the end of the year, six in a leap year, were holidays named after virtues and the Revolution.
Each year began on the day of the September equinox as seen at the Paris Observatory. That astronomical rule is why year lengths follow no simple pattern in the original calendar. Years III, VII and XI were 366 days long.
The historical range
Napoleon restored the Gregorian calendar from 1 January 1806, so Year XIV ends on 10 Nivôse. Later proposals for a fixed leap year rule, and the use of the calendar during the Paris Commune of 1871, are not the calendar of this tool. The page covers the 13 years when it was in force.
The year start dates here agree with the equinox rule. The weekday of the Gregorian date is shown only so that you can place the day in a normal week. The ten-day decade was the working week of the Republic, and a rest day came once every ten days.
Assumptions and limits
- The range is 22 September 1792 to 31 December 1805, when the calendar was in official use in France.
- Month names are shown with their French accents, and the extra days as the complementary days at the end of the year.
- Dates use the proleptic Gregorian calendar.
- Nothing is uploaded.
Frequently asked questions
Why does the range stop in 1805?
The calendar was dropped on 1 January 1806. Later dates would only be projections, so the tool does not offer them.
Which years were leap years?
Years III, VII and XI had 366 days. Year IV began on 23 September 1795 after a leap Year III.
What are the extra days?
The five or six days after the 12th month. They are shown as month 13 and are named days such as the Day of Virtue.
Can I enter the year in Roman numerals?
Enter it as a number from 1 to 14. The result is shown in Roman numerals, as the calendar was written.