On this day in Tudor history, 10th April 1585, Pope Gregory XIII died from a fever. He was succeeded by Pope Sixtus V.

Pope Gregory is known for his reform of the calendar. He introduced what is now called the Gregorian Calendar, or Western or Christian Calendar, replacing the Julian Calendar, which had been used since 45 BC.

But why was this reform needed and how was it done?

Find out more about it, and how England didn’t use it until the 18th century, in today’s talk.