Gregorian Calendar

The Gregorian Calendar was introduced by Pope Gregory XIII in 1582. It is the calendar that is used in most of the world. Prior to the introduction of the Gregorian Calendar, the Julian Calendar was in use. One of the changes introduced by the Gregorian Calendar was a small reduction in the number of leap years.

Although the Gregorian Calendar is named after Pope Gregory XIII, it is an adaptation of a calendar designed by Luigi Lilio. He was an Italian astronomer, doctor and philosopher. He died in 1576, six years before his calendar was officially introduced.

The Gregorian Calendar replaced the Julian Calendar. Before the Julian Calendar, the Roman Calendar was used. Other calendars include the Persian and Mayan.