Advent is a season of penance, and of preparation by the Faithful for the spiritual joy of Christmas. It is a time when the Church admonishes us to lift our hearts to God and to trust in Him who is to free us from our sins. As Advent is a season of penance, the colour of the vestments used at its seasonal Masses is violet and the altar is not decorated with flowers, except on the third Sunday which is called Gaudete Sunday or "Rejoice Sunday", because the Introit of the Mass of that day reminds us of the near approach of Our Lord's birth: "Rejoice in the Lord always; again I say rejoice. Let your modesty be known to all men. The Lord is nigh".

Christmas derives its name, "Christ's Mass," from the Mass offered in honour of the Birth of Christ. Its early English form was written as "Christes Maesse," and in the course of the change of the English language it eventually became Christmas. In the earliest days of the Church this feast did not exist. Greater stress was placed on the Feast of the Epiphany, because it commemorates the day on which our Saviour was made known to the Gentiles, when the Wise Men came to adore Him. The Feast of the Nativity came gradually into existence in the fourth century. Its first mention is made by the great Christian writer, Clement of Alexandria, about the year 200, and shows that it was celebrated on May 20. About the year 300, the Latin Church began to observe it on December 25, because an ancient tradition assigns that day as the probable date of the Birth of our Saviour.