The Gregorian Calendar is Adopted in 1582

by Heather R. Darsie On 15 October 1582, the Gregorian calendar was decreed via papal bull. Pope Gregory XIII, under the bullĀ Inter gravissimas or Of Great Importance, corrected calculation of a year from 365.25 days in the Julian calendar to 365.2422 days in Gregorian. Also, the Julian calendar had 100 leap days over 400 years, whereas the proposed Gregorian would have only 97. Most centennial … Continue reading The Gregorian Calendar is Adopted in 1582