[Picture: French Republican Calendar of 1794, drawn by Louis-Philibert Debucourt]
The riots and violence persisted until the Convention, charged with writing a new constitution, met on 20 September 1792 and became the new de facto government of France. The next day it abolished the monarchy and declared a republic. This date was later retroactively adopted as the beginning of Year One of the French Revolutionary Calendar.
The calendar was designed by the politician and agronomist Charles Gilbert Romme, although it is usually attributed to Fabre d'Églantine, who invented the names of the months. Years appear in writing as Roman numerals (usually), counted from the beginning of the 'Republican Era', 22 September 1792