calendars

The Gregorian calendar is the most widely used calendar in the world today. It was first proposed by the Calabrian doctor Aloysius Lilius, and decreed by Pope Gregory XIII, after whom it was named, on 24 February 1582 by the papal bull Inter gravissimas.

It is a reform of the Julian calendar and continues the year numbering system of the Julian calendar, counting years from the traditional Incarnation of Jesus. Years after this date are given the designation "anno Domini" (AD),This era was created in the 6th century by Roman monk Dionysius Exiguus or "Common Era" (CE); years before this date are labeled "before Christ" (BC), or "Before the Common Era" (BCE).