Gregory XIII was Pope from 1572 to 1585, and his influence can be seen in the reformation of the liturgical calendar that took place during his papacy. Although there are not many direct synonyms for his name, some terms that may be associated with him include the Counter-Reformation, the Council of Trent, and the Gregorian calendar. The Counter-Reformation was a period of Catholic revival and reform that sought to combat the rise of Protestantism; the Council of Trent was a major council of the Catholic Church that occurred during Gregory XIII's time as Pope; and the Gregorian calendar is the calendar used by much of the modern world, which was introduced by Pope Gregory XIII in 1582.