Extraordinary Jubilee functions and processions
The extraordinary jubilees described by Gaetano Moroni (1802-1883), author of the most famous Dizionario di erudizione storico-ecclesiastica, were proclaimed by pontiffs from the sixteenth century onwards for special occasions, at difficult times, or to celebrate the beginning of a pontificate. They lasted varying lengths of time and were often only local in scope (more than seventy of them were held). Between 1933 and 1983, and again in 2016, there have been a number of extraordinary jubilees whose duration, scope and ceremony are identical to ordinary universal jubilees, qualifying them as true Holy Years
Gaetano Moroni, Funzioni e processioni pei giubilei straordinarii, in: Id., Le cappelle pontificie, cardinalizie e prelatizie. Opera storico liturgica..., Venezia 1841