Pope Gregory XIII

Pope Gregory XIII (; 7 January 1502 – 10 April 1585), born Ugo Boncompagni, was the head of the Catholic Church from 13 May 1572 to his death in 1585. He is best known for commissioning and being the namesake for the Gregorian calendar, which remains the internationally accepted civil calendar to this date.
Early life.
Ugo Boncompagni was born in 1502, in Bologna. 
Bishop.
Pope Paul IV appointed him Bishop of Viesti in 1558.
Cardinal.
In 1564, he was made a cardinal by Pope Pius IV. 
Pope.
Cardinal Boncompagni was elected Pope at age 70; and he chose to be called Gregory XIII.
Pope Gregory was involved in Italian and European political disputes.
He founded the Gregorian University in Rome.
In the last year of his life, Gregory received an embassy from Japan.
Gregorian calendar.
Pope Gregory is famous for his correction of mistakes in the Julian calendar. To accomplish the necessary changes, the Gregorian calendar skipped ten days between 4 October 1582 and 15 October 1582.