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French Republican Calendar Converter — Revolutionary Calendar | LazyTools
Historical Calendar Tool

French Republican Calendar Converter — Revolutionary Calendar

Convert any Gregorian date to the French Republican Calendar — the revolutionary calendar used by France from 22 September 1792 to 31 December 1805. Each month was named after a natural phenomenon of the season: Vendémiaire (grape harvest), Thermidor (summer heat) and Fructidor (fruits). Furthermore, the tool shows the day of the decade (the Republican 10-day week), the Roman numeral year and a reference grid of all 12 months with their natural meanings.

Nature-named monthsDay of decade (décade)Roman numeral yearSansculottides handledMonth meanings grid
The 12 Republican months and their meanings

How to use the French Republican Calendar Converter

1
Enter any Gregorian date
Click the date field and select any date from 22 September 1792 onwards. Furthermore, entering a date before 22 September 1792 triggers a notification — the Republican Calendar did not exist before the French Revolution began that day. Dates after 1805 are converted as an educational extension.
2
Click Convert to French Republican Calendar
The result shows the Republican day, month name, Roman numeral year and day of the decade. Furthermore, the month meaning appears in the table — each month name references the natural world of that season in France.
3
Understand the 10-day week (décade)
The Republican Calendar replaced the 7-day week with a 10-day decade. Furthermore, the ten days were named Primidi, Duodi, Tridi, Quartidi, Quintidi, Sextidi, Septidi, Octidi, Nonidi and Décadi. The 10th day (Décadi) was the day of rest — replacing Sunday.
4
Check the Sansculottides
Each Republican year has 12 months of 30 days (360 days) plus 5 or 6 extra days at the end. Furthermore, these were called the Sansculottides — named after the sans-culottes, the working-class revolutionaries. Each Sansculottide day had a name: Virtue, Genius, Labour, Opinion, Rewards and (in leap years) Revolution.
5
Explore the month meanings grid
The reference grid below the widget shows all 12 months with their English meaning and approximate Gregorian start date. Furthermore, this shows how the Republican Calendar tried to replace religious and royalist names with secular, nature-based terminology.

The 12 Republican months and the Sansculottides

The French Republican Calendar divided the year into four seasonal groups of three months each. Furthermore, each month name reflected the natural world of that season in France — rejecting the Roman and religious names of the traditional calendar.

SeasonMonthsNatural themeGregorian approx.
AutumnVendémiaire, Brumaire, FrimaireHarvest, mist, frostSep–Dec
WinterNivôse, Pluviôse, VentôseSnow, rain, windDec–Mar
SpringGerminal, Floréal, PrairialSeeds, flowers, meadowsMar–Jun
SummerMessidor, Thermidor, FructidorHarvest, heat, fruitsJun–Sep
Year-endSansculottides (5–6 days)Revolutionary virtues~Sep 17–22

The 10-day décade — replacing the 7-day week

One of the most radical changes in the Republican Calendar was replacing the 7-day week with a 10-day décade. Furthermore, this removed the Sunday day of rest — replacing it with Décadi, the 10th day. Moreover, the decade names (Primidi through Décadi) were based on Latin number words rather than planetary names. This proved deeply unpopular — a key reason the calendar was abandoned after 13 years.

How the French Republican Calendar works

The Republican Calendar year starts at the autumnal equinox — originally calculated astronomically. Furthermore, the simplified tabular version used here anchors Year I to 22 September 1792. Each year has 12 months of exactly 30 days plus 5 or 6 Sansculottide days at year-end.

Republican year = floor((JDN − 2375839) / 365) + 1
Epoch JDN = 2375839 (22 September 1792 Gregorian)
Republican month = floor((day-of-year) / 30) + 1 (months 1–12)
Day of decade = day mod 10 (1–10; Décadi = 10th = day of rest)
Leap year = every 4th Republican year (following the equinox pattern)

Why the calendar was abandoned in 1806

Napoleon abolished the Republican Calendar effective 1 January 1806 (11 Nivôse Year XIV). Furthermore, the calendar had been unpopular for disrupting the 7-day religious week. Moreover, the Concordat of 1801 — Napoleon's peace with the Catholic Church — made restoring Sunday as the day of rest politically necessary.

Worked example: the fall of Robespierre

The "Thermidorian Reaction" — the fall of Maximilien Robespierre — occurred on 9 Thermidor Year II. What Gregorian date is this?

Republican dateGregorian equivalent
9 Thermidor Year II27 July 1794
18 Brumaire Year VIII9 November 1799 (Napoleon's coup)
14 Fructidor Year IX1 September 1801
9 Thermidor Year II = 27 July 1794 — the day Robespierre was arrested and the Reign of Terror ended. Furthermore, "Thermidorian" entered the political vocabulary as a term for a conservative reaction following a radical revolutionary period. The month name Thermidor — meaning "summer heat" — is still recognisable in political history today.

What is the French Republican Calendar?

The French Republican Calendar was France's official calendar from 22 September 1792 to 31 December 1805. Furthermore, it broke completely with the Gregorian calendar's religious and monarchical associations. The revolutionary government replaced saints' days with nature-themed names and eliminated the 7-day week. Furthermore, a 10-day décade replaced it.

A committee including the poet Fabre d'Églantine created the calendar. Furthermore, each day received a plant, animal or tool name rather than a saint's name. Moreover, Year I began on 22 September 1792 — when the First French Republic was proclaimed.

Legacy of the Republican Calendar

The French Republican Calendar left a lasting cultural mark. Furthermore, "Thermidor" entered political vocabulary as a term for a conservative reaction to revolution — used by Leon Trotsky to describe the Stalinist period. "Germinal" was adopted by Émile Zola as the title of his novel about coal miners. Moreover, "Brumaire" became famous through Marx's essay "The Eighteenth Brumaire of Louis Napoleon" — a study of how history repeats.

Why the French Republican Calendar matters

Historical research on the French Revolutionary period requires Republican Calendar literacy. Furthermore, primary sources from 1792 to 1805 use Republican dates exclusively. Converting 18 Brumaire Year VIII to 9 November 1799 reveals Napoleon's coup; 9 Thermidor Year II becomes 27 July 1794, the end of the Reign of Terror. Moreover, 18 Brumaire Year VIII (9 November 1799) is Napoleon's coup — central to Western political history.

The calendar represents one of history's most ambitious uses of timekeeping as a tool of cultural revolution. Furthermore, replacing saints' days with plants and tools attempted to reframe daily consciousness as secular. Moreover, its abandonment after 13 years shows the limits of top-down calendar reform against deep social habit.

The Republican Calendar in culture

The month names Germinal, Thermidor and Brumaire remain recognisable in European political discourse. Furthermore, "Thermidorian" entered political science as a term for counter-revolutionary consolidation.

Frequently asked questions

The French Republican Calendar was officially in use from 22 September 1792 (Year I) to 31 December 1805 (11 Nivôse Year XIV), when Napoleon abolished it by decree. Furthermore, it was briefly revived during the Paris Commune from 18 March to 28 May 1871 — a period of approximately 71 days. Otherwise, the Gregorian calendar remained standard in France outside this period.
The 10-day décade replaced the 7-day week, and Décadi (the 10th day) replaced Sunday as the day of rest. Furthermore, this was deeply unpopular — it meant only 3 days off per month instead of approximately 4. Moreover, workers and craftspeople still observed Sunday in practice, creating a dual calendar situation that undermined the Republican system's adoption.
The Sansculottides are the 5 or 6 extra days at the end of each Republican year, following the 12th month (Fructidor). Furthermore, they were named after the sans-culottes — the working-class militants who wore long trousers rather than aristocratic knee-breeches. Each day had a theme: Virtue, Genius, Labour, Opinion and Rewards, with a 6th day (Revolution) added in Republican leap years. Moreover, the Sansculottides were celebrated as revolutionary festivals rather than ordinary work days.
The committee that created the calendar — led by poet Fabre d'Églantine — believed that replacing saints' names with natural phenomena would secularise daily life and break the psychological hold of religion on the population. Furthermore, each month name reflected the agricultural and meteorological reality of that season in France. Moreover, each of the 360 named days within the months was assigned a plant, animal, tool or mineral — turning the entire calendar into a secular almanac of the natural world.
Each Republican month has exactly 30 days divided into three 10-day periods called décades. Furthermore, the ten days of each décade are: Primidi, Duodi, Tridi, Quartidi, Quintidi, Sextidi, Septidi, Octidi, Nonidi and Décadi. Décadi was the day of rest. Moreover, this system produced 36 décades per year (plus the 5-6 Sansculottide days) and was intended to increase economic productivity by reducing rest days from approximately 52 Sundays to 36 Décadis.

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