The Gregorian calendar was decreed in 1582 by the papal bull Inter gravissimas
by Gregory ... at the bottom it was signed with papal authorization and by Lilio (
Con licentia delli Superiori... et pe...
The Gregorian calendar was first introduced in 1582, however, different countries
changed from the Julian Calendar at different times.
The Difference Between Julian and Gregorian Calendars. The Gregorian
Calendar was first introduced by Pope Gregory XIII - which is how the calendar
got its ...