The Gregorian Reformation of the Calendar

Abstract

THIS week is the 350th anniversary of the reform of the calendar ordained by Pope Gregory. The day following Oct. 4, 1582, was called Oct. 15. It is not always remembered that, in addition to the calendar changes, greatly improved lunar tables were introduced for the purpose of computing the date of Easter. An article in the Southwark Record notes that the necessary calculations were executed by Luigi Giglio (Aloysius Lilius), Ignatius Danti, and Christopher Clavius. It also points out that the ten days stolen from October are now being slowly repaid, as the ‘Summer Time’ reckoning gives October an additional hour each year.