The Solemnity of Our Lord Jesus Christ, King of the Universe, celebrated this year on Nov. 20, also is referred to as the Feast of Christ the King, Christ the King Sunday, or Reign of Christ Sunday.

While the concept of Jesus Christ being King is as old as the Gospels, the feast is fairly recent in the Roman Catholic calendar. 

The feast was introduced in the Western liturgical calendar in 1925 by Pope Pius XI, via the encyclical "Quas Primas." Pope Pius XI was about to close the Jubilee year of 1925 in the context of the growing secularist nationalism that followed the fall of European kingdoms after World War I, and decided to establish the solemnity to point to a king "of whose kingdom there shall be no end.” 

A key passage from Quas Primas provided Catholic preachers with a helpful synopsis. “This kingdom (of Christ) is spiritual and is concerned with spiritual things…. The gospels present this kingdom as one which men prepare to enter by penance, and cannot actually enter except by faith and by baptism, which, though an external rite, signifies and produces an interior regeneration. This kingdom is opposed to none other than to that of Satan and to the power of darkness. It demands of its subjects a spirit of detachment from riches and earthly things, and a spirit of gentleness. They must hunger and thirst after justice, and more than this, they must deny themselves and carry the cross.”

Pope Pius XI established the feast to be celebrated on the last Sunday of October, so that it would always take place before the celebration of the solemnity of All Saints. But in the new liturgical calendar of 1970, its Roman Rite observance was moved to the last Sunday of Ordinary Time. Therefore, the earliest date on which it can occur is Nov. 20 and the latest is Nov. 26.