The papal bull () was issued on 24 February 1582 (year 1581 in Florentine Easter-based reckoning), ordering Catholic clergy to adopt the new calendar, and exhorting all Catholic sovereigns to do the same. The year 2010 was the 500th year since the Lilius' birth; several activities were organized by Italian astronomers in order to recognize the great work performed by him. In particular, in Torretta di Crucoli (Crotone, Italy), a new astronomical group was created and dedicated to Luigi Lilio. Notes References . . . External links Circolo Astrofili Luigi Lilio Torretta 1510s births 1576 deaths Academic staff of the University of Perugia 16th-century Italian astronomers Chronologists People from the Province of Crotone Gregorian calendar