Pope Gregory XIII, born Ugo Boncompagni in 1502, served as the head of the Roman Catholic Church from 1572 until his death in 1585. He is best known for instituting the Gregorian calendar, which corrected inaccuracies in the previous Julian calendar. This reform aimed to align the calendar year with the solar year and improve the timing of important religious events. During his papacy, Gregory XIII also focused on the Counter-Reformation, supporting the Jesuits and promoting Catholic education. He worked to strengthen the Church's influence in Europe and was involved in various political matters, including the French Wars of Religion.