Sansculottides

The Sansculottides (; also Epagomènes; French "Sans-culottides", "Sanculottides", "jours complémentaires", "jours épagomènes") are holidays following the last month of the year on the French Republican Calendar which was used following the French Revolution from approximately 1793 to 1805. 
The Sansculottides, named after the sans-culottes, append the twelve, 30-day months of the Republican Calendar with five complementary days in a common year or six complementary days in a leap year so that the calendar year would approximately match the tropical year. They follow the last day of Fructidor, the last month of the year, and precede the first day of Vendémiaire. 
The Sansculottides belong to the summer quarter. They begin on 17 or 18 September and approximately end on the autumn equinox, on 22 or 23 September on the Gregorian calendar.
History.
In the decree of 5 October 1793 ("le 14 du 1er mois de l'an II"; later: "le 14 Vendémiaire de l'an II") by the National Convention, the days following the last month of the year were named "jours complémentaires" and numbered serially. Only the leap day ("jour intercalaire") received a name:
The other days, decades, and months were also serially numbered. 
On 24 October ("le 3 du 2e mois"; later: "le 3 Brumaire") of the same year, the poet Philippe-François-Nazaire Fabre, known as Fabre d'Églantine, made public his dislike of this naming convention ("le premier jour de la première décade du premier mois de la première année"). He suggested proper names for the months, the days of the months, and the days of the decades. For the "jours complémentaires", he introduced the name "Sansculottides". The individual days should have the following names:
According to the proposal by Fabre d'Églantine:
On 24 November 1793 these proposals were accepted with slight modifications. It was decided that the name should be written "fêtes Sansculotides" (one 't'). The alternate spellings "Sans-culotides" and "Sans-culottides" were also used. The "fête des actions" was shifted to the first place and named "fête de la vertu". The "fête des récompenses" went to the last place and the leap year day regained its old name:
On 24 August 1795 ("le 7 Fructidor de l'an III"), the Sansculottides were renamed again to "jours complémentaires" (Complementary Days). The "fête du travail" was also known as the "fête du labour". The "fête de l'opinion" was also termed "fête de l'option" (Celebration of Choice) or "fête de la raison" (Celebration of Reason).
The Basque translation of the calendar for 1799 simply names the "bethagail-egunak" as "bethagail-legun", "bethagail-bigun"... ("complementary primidi", "complementary duodi"...).