Overview and origins
Sylvain Maréchal, prominent anticlerical atheist, published the first edition of his Almanach des Honnêtes-gens (Almanac of Honest People) in 1788. On pages 14–15 appears a calendar, consisting of twelve months. The first month is "Mars, ou Princeps" (March, or First), the last month is "Février, ou Duodécembre" (February, or Twelfth). (The months of September [meaning "the seventh"] through December [meaning "the tenth"] are already numeric names, although their meanings do not match their positions in either the Julian or the Gregorian calendar since the Romans changed the first month of a year from March to January.) The lengths of the months are the same; however, the 10th, 20th, and 30th are singled out of each month as the end of a décade (group of ten). Individual days were assigned, instead of to the traditional saints, to people noteworthy for mostly secular achievements; 25 December is assigned to both Jesus and Newton.
Later editions of the almanac would switch to the Republican Calendar.
A copy of the French Republican Calendar in the Historical Museum of Lausanne
The days of the French Revolution and Republic saw many efforts to sweep away various trappings of the ancien régime (the old feudal monarchy); some of these were more successful than others. The new Republican government sought to institute, among other reforms, a new social and legal system, a new system of weights and measures (which became the metric system), and a new calendar. Amid nostalgia for the ancient Roman Republic, the theories of the Enlightenment were at their peak, and the devisers of the new systems looked to nature for their inspiration. Natural constants, multiples of ten, and Latin as well as Ancient Greek derivations formed the fundamental blocks from which the new systems were built.
The new calendar was created by a commission under the direction of the politician Charles-Gilbert Romme seconded by
Claude Joseph Ferry and Charles-François Dupuis. They associated with their work the chemist Louis-Bernard Guyton de Morveau, the mathematician and astronomer Joseph-Louis Lagrange, the astronomer Joseph Jérôme Lefrançois de Lalande, the mathematician Gaspard Monge, the astronomer and naval geographer Alexandre Guy Pingré, and the poet, actor and playwright Fabre d'Églantine, who invented the names of the months, with the help of André Thouin, gardener at the Jardin des Plantes of the Muséum National d'Histoire Naturelle in Paris. As the rapporteur of the commission, Charles-Gilbert Romme presented the new calendar to the Jacobin-controlled National Convention on 23 September 1793, which adopted it on 24 October 1793 and also extended it proleptically to its epoch of 22 September 1792. It is because of his position as rapporteur of the commission that the creation of the republican calendar is attributed to Romme.
The calendar is frequently named the "French Revolutionary Calendar" because it was created during the Revolution, but this is moderate of a misnomer. Indeed, there was initially a debate as to whether the calendar should celebrate the Great Revolution, which began in July 1789, or the Republic, which was established in 1792. Immediately following 14 July 1789, papers and pamphlets started calling 1789 year I of Liberty and the following years II and III. It was in 1792, with the practical problem of dating financial transactions, that the legislative assembly was confronted with the problem of the calendar. Originally, the choice of epoch was either 1 January 1789 or 14 July 1789. After some hesitation the assembly decided on 2 January 1792 that all official documents would use the "era of Liberty" and that the year IV of Liberty started on 1 January 1792. This usage was modified on 22 September 1792 when the Republic was proclaimed and the Convention decided that all public documents would be dated Year I of the French Republic. The decree of 2 January 1793 stipulated that the year II of the Republic began on 1 January 1793; this was revoked with the introduction of the new calendar, which set 22 September 1793 as the beginning of year II. The establishment of the Republic was used as the epochal date for the calendar; therefore, the calendar commemorates the Republic, not the Revolution. In France, it is known as the calendrier républicain as well as the calendrier révolutionnaire.
French coins of the period naturally used this calendar. Many show the year (French: an) in Arabic numbers, although Roman numerals were used on some issues. Year 11 coins typically have a "XI" date to avoid confusion with the Roman "II".
The French Revolution is usually considered to have ended with the coup of 18 Brumaire, Year VIII (9 November 1799), the coup d'état of Napoleon Bonaparte against the established constitutional regime of the Directoire.
The Concordat of 1801 re-established the Roman Catholic Church as an official institution in France, although not as the state religion of France. The concordat took effect from Easter Sunday, 28 Germinal, Year XI (8 April 1802); it restored the names of the days of the week to the ones from the Gregorian Calendar, and fixed Sunday as the official day of rest and religious celebration. However, the other attributes of the republican calendar, the months, and years, remained as they were.
The French Republic ended with the coronation of Napoleon I as Empereur des Français (Emperor of the French) on 11 Frimaire, Year XIII (2 December 1804), but the republican calendar would remain in place for another year. Napoleon finally abolished the republican calendar with effect from 1 January 1806 (the day after 10 Nivôse Year XIV), a little over twelve years after its introduction. It was, however, used again briefly during the short period of the Paris Commune, 6–23 May 1871 (16 Floréal–3 Prairial Year LXXIX).
L AN 2 DE LA REPUBLIQUE FR (Year 2 of the French Republic) on a barn near Geneva
Years appear in writing as Roman numerals (usually), with epoch 22 September 1792, the beginning of the "Republican Era" (the day the French First Republic was proclaimed, one day after the Convention abolished the monarchy). As a result, Roman Numeral I indicates the first year of the republic, that is, the year before the calendar actually came into use. By law, the beginning of each year was set at midnight, beginning on the day the apparent autumnal equinox falls at the Paris Observatory.
There were twelve months, each divided into three ten-day weeks called décades. The tenth day, décadi, replaced Sunday as the day of rest and festivity. The five or six extra days needed to approximate the solar or tropical year were placed after the months at the end of each year and called complementary days. This arrangement was an almost exact copy of the calendar used by the Ancient Egyptians, though in their case the beginning of the year was marked by summer solstice rather than autumn equinox.
A period of four years ending on a leap day was to be called a "Franciade". The name "Olympique" was originally proposed but changed to Franciade to commemorate the fact that it had taken the revolution four years to establish a republican government in France.
The leap year was called Sextile, an allusion to the "bissextile" leap years of the Julian and Gregorian calendars, because it contained a sixth complementary day.
Each day in the Republican Calendar was divided into ten hours, each hour into 100 decimal minutes, and each decimal minute into 100 decimal seconds. Thus an hour was 144 conventional minutes (more than twice as long as a conventional hour), a minute was 86.4 conventional seconds (44% longer than a conventional minute), and a second was 0.864 conventional seconds (13.6% shorter than a conventional second).
Clocks were manufactured to display this decimal time, but it did not catch on. Mandatory use of decimal time was officially suspended 7 April 1795, although some cities continued to use decimal time as late as 1801.
The numbering of years in the Republican Calendar by Roman numerals ran counter to this general decimalization tendency.