Brumaire: The Republican Calendar
Offers a history of the French Republican Calendar, its creators, and calendars in general.
FamilySearch: French Republican Calendar
Explains the history and principles of the French Republican calendar, and offers instructions for converting dates to the standard Gregorian calendar.
French Republican Calendar, The
Offers a history of the French Republican calendar, from which Christian superstition was stripped in the name of Reason.
Wikipedia: French Republican Calendar
Article describing the French Republican Calendar or French Revolutionary Calendar, used by the French government for about twelve years from late 1793.