The term "Year One" in political history usually refers to the institution of radical, revolutionary change. This usage dates from the time of the French Revolution: after the abolition of the French monarchy (20 September 1792), the National Convention instituted the new French Revolutionary Calendar, declaring that date as the beginning of the Year I of the French Republic.
Frank Miller adopted this term for his DC Comics comic-book story arc Batman: Year One (Batman #404–407), retelling the Batman origin story in the "Post-Crisis" DC Universe. This comic established the expression DC later used in other comic books. Year One books include: