The Christmas Liturgy is one of the most ancient in the universal Church - both East and West celebrating with special joy and customs.
The Roman Catholic Church:
One of the hallmarks of the Christmas liturgy according to the traditional Roman Rite is the celebration of three distinct Masses on this day preceded by a Vigil liturgy on Christmas Eve, the highlight of which is the solemn reading of the Martyrology at Prime:
In the year 5199th from the creation of the world, when in the beginning God created the heavens and the earth, in the year 2959th from the flood, in the year 2015th from the birth of Abraham, in the year 1510th from the going forth of the people of Israel out of Egypt under Moses, in the year 1032th from the anointing of David as King, in the 65th week according to the prophecy of Daniel, in the 194th Olympiad, in the 752nd from the foundation of the city of Rome, in the 42nd year of the reign of the Emperor Octavian Augustus, in the 6th age of the world, while the whole earth was at peace, Jesus Christ, Himself Eternal God and Son of the Eternal Father, being pleased to hallow the world by His most gracious coming, having been conceived of the Holy Ghost, and when nine months were passed after His conception, [all kneel down] was born of the Virgin Mary at Bethlehem of Juda made Man, Our Lord Jesus Christ was born according to the flesh."
In addition to particular rubrical observances made during the season of Advent, the most visible of which being the Advent Wreath and the use of violet and rose vestments, Vespers during the final seven days of the season include the famous “O Antiphons” that are chanted before and after the Magnificat. These ancient hymns, which date to at least the 6th Century, point toward the Nativity of our Lord. Joining these anticipatory antiphons are two recited at Lauds on December 21 and 23 respectively, the latter of which assuring the faithful, “Behold, all things are fulfilled, which were spoken by the Angel to the Virgin Mary.”
The Byzantine Catholic Church:
The Byzantine Rite, which traditionally celebrates Christmas on January 7 according to the Julian Calendar, includes its own special ceremonies leading up to the Nativity. On Christmas Eve, all of the little hours (Prime, Terce, Sext, and None according to the Roman Rite) are recited as a single service known as the Royal Hours due to the service having historically been attended by the Byzantine Emperor and his court at the great cathedral of Hagia Sophia in Constantinople. Unlike the rest of the liturgical year, each hour includes an Old Testament, Epistle, and Gospel reading, along with special Psalms appointed specifically for the Nativity.
In the evening, a special Vesperal Divine Liturgy is appointed with a wider array of Old Testament readings that prophesize the coming of Jesus Christ into the world. Finally, historic monastic usage, which today is still honored in some parishes, calls for the celebration of a unique All-Night Vigil with Great Compline replacing Vespers, followed by Matins and the First Hour (Prime) of Christmas. It is at the Vigil, rather than the Vesperal Liturgy, when Christmas truly begins in the Byzantine Rite. This is why it is not forbidden for the faithful to attend and commune at both the Vesperal Liturgy celebrated on December 24 and the Divine Liturgy celebrated on December 25. Both liturgies constitute an organic whole rather than two “options” from which Christians can choose at their convenience.
There are only two other times during the Byzantine liturgical year where the daily order of services are prescribed to be celebrated in this manner: Theophany and Pascha (Easter). By “interrupting” the regular liturgical flow for these feasts, the Byzantine Rite calls particular attention to their importance to the Mystery of Salvation and the glory of Jesus Christ. Moreover, like the Roman Rite, the Byzantine Rite wishes to make the transition from Advent to the Nativity as solemn as possible in order to commemorate the greatest event in human history.
In these final days of preparation for the birth of our Lord and Savior Jesus Christ, let us resist the temptations of consumerism and revelry in order to commend ourselves to God and raise up prayers for the protection of Holy Mother Church.