The Solemnity of Our Lord Jesus Christ, King of the Universe (commonly referred to as the Feast of Christ the King) is a relatively recent addition to the western liturgical calendar, having been instituted in 1925 by Pope Pius XI. In 1970 its observance was moved to the last Sunday of Ordinary Time and adopted by Anglicans, Lutherans, and many other Protestants along with the new Revised Common Lectionary; it is also observed in this same position as the last Sunday of the church year, the Sunday before the First Sunday of Advent, by Western rite parishes of the Russian Orthodox Church Outside of Russia. Roman Catholics adhering to the Extraordinary Form of the Roman Rite (as permitted under the motu proprio Summorum Pontificum) use the General Roman Calendar of 1960, and as such continue to observe the feast on its original date of the last Sunday of October.
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Image is of the Christ Pantocrator mosaic from Hagia Sophia.