The lesson discusses the radical changes during the Reign of Terror in France, focusing on the Jacobins’ efforts under Maximilien Robespierre to secularize society by abolishing the Gregorian calendar and adopting a new one starting from September 22, 1792, marking the establishment of the French Republic. Robespierre, although a leading figure, was against completely abolishing religion, believing a form of worship was necessary for the state. This period was marked by intense anti-clerical measures and a shift from monarchy to a republic, illustrating efforts to control and transform cultural and religious institutions.