The Gregorian calendar is the most widely used civil calendar in the world.[Note 1] It is named after Pope Gregory XIII, who introduced it in October 1582. The calendar spaces leap years to make the average year 365.2425 days long, approximating the 365.2422 day tropical year that is determined by the Earth's revolution around the Sun. Our theme song was written and performed by Anna Bosnick. If you’d like to support the show on a per episode basis, you can find our Patreon page here. Be sure to check our website for more details.