Days set apart by the Church for giving special honor to God, the Savior, angels, saints, and sacred mysteries and events. Some are fixed festivals, such as Christmas and the Immaculate Conception; others are movable, occurring earlier or later in different years. Festivals are now divided, since the Second Vatican Council, into solemnity (solemnitas), feast (festum), and memorial (memoria) in descending order of dignity. Memorials are further classified as prescribed or optional. Below these are ferial, or week, days with no special ritual rank. And in a class by themselves are the Sundays of the year, and the various liturgical seasons, such as Advent and Lent. All of these represent what is called "sacred times," whose religious purpose is to keep the faithful mindful throughout the year of the cardinal mysteries and persons of Christianity.