The Gregorian Calendar Is Based On __________.. The gregorian calendar is used throughout most of the modern world. Pope gregory xiii began the modern calendar 400 years ago in order to correct the accumulating drift in the julian calendar and keep easter in the spring
Pope gregory xiii issued a papal bull, inter gravissimus on february 24, 1582 that established the gregorian calendar as the new and official calendar of the catholic world. The gregorian calendar is the most used calendar system in the world today.