In his encyclical Quas Primas, Pope Pius XI instituted The Feast of Christ the King in 1925, to be celebrated throughout the universal church. He connected the increasing denial of Christ as king to the rise of secularism throughout much of Europe. Pius XI and the rest of the Christian world witnessed the rise of non-Christian (or nominally Christian) dictatorships throughout Europe and saw Catholics being persuaded by these earthly leaders. These dictators also often attempted to assert authority over the Church. Just as the Feast of Corpus Christi was instituted, devotion to the Eucharist was at a low point. The Feast of Christ the King was instituted during a time when respect for Christ and the Church was waning, and when the feast was needed most.
Today, individualism has been embraced to such an extreme, that for many, the only authority is the individual self. The idea of Christ as ruler is rejected in such a strongly individualistic system. Also, many balk at the idea of kings and queens, believing them to be antiquated and possibly oppressive. Some even reject the titles of "Lord" and "King" for Christ because they believe that such titles are borrowed from oppressive systems of government. However true, these statements might be (some kings have been oppressive), these individuals miss the point: Christ's kingship is one of humility and service.
Jesus said, “You know that those who are recognized as rulers over the Gentiles lord it over them, and their great ones make their authority over them felt. But it shall not be so among you. Rather, whoever wishes to become great among you will be your servant; whoever wishes to be first among you will be the slave of all. For the Son of Man did not come to be served, but to serve and to give his life as a ransom for many.” (Mark 10:42-45, NAB) Pilate said to Jesus, "Are you the King of the Jews?"... Jesus answered, "My kingdom does not belong to this world. If my kingdom did belong to this world, my attendants would be fighting to keep me from being handed over to the Jews. But as it is, my kingdom is not here." So Pilate said to him, "Then you are a king?" Jesus answered, “You say I am a king. For this I was born and for this I came into the world, to testify to the truth” (John 18:33b, 36-37) Thus, Jesus knew the oppressive nature of secular kings, and in contrast to them, he connected his role as king to humble service and commanded his followers to be servants as well. When we celebrate Christ as King, we are not celebrating an oppressive ruler, but one willing to die for humanity and whose "loving-kindness endures forever." Christ is the king that gives us true freedom, freedom in Him. Christ the King Sunday used to be celebrated on the last Sunday of October, but since the calendar reforms of 1969, the feast falls on the last Sunday of Ordinary Time, which is the Sunday before Advent. It is fitting that the feast celebrating Christ's kingship is observed right before Advent when we liturgically wait for the promised Messiah (King).