The season of Advent is past; the period of anticipation is complete. The solemnity of the Lord’s birth celebrates the mystery of the incarnation by which the Word of God humbled himself to share our humanity, in order that he might enable us to become sharers in his divinity.
The second Mass of Christmas Day is the Mass at Dawn, traditionally called the Shepherds’ Mass because the gospel text recounts the visit of the shepherds. Just as the shepherds went eagerly to the crib to adore the Lord and to receive his great gift of light, so we also go to the altar where the same Lord comes just as truly to us. The theme of light is prominent in this Mass. Outside, the natural light is increasing. In Bethlehem, the Light is manifested to a few more men. Over and over in the Mass texts, light is mentioned: The Introit begins, “A Light shall shine upon us this day; for the Lord is born to us.”
Since the 18th century, it has been commonly taught that the date of Christmas was set in order to counteract a pagan Roman festival of Dies Natalis Solis Invicti, or “Birthday of the Unconquered Sun,” which was celebrated on December 25th. Just after the winter solstice, the year’s shortest day, when it seems that the nights are so long that they will suppress the light of day, Sol Invictus, the Roman sun god, begins to regain strength and the days start to lengthen again — a victory that was cause for rejoicing. It is therefore thought that Christians chose this day because Jesus is one with the true God, who conquers the power of darkness.
The origin of the calendar date, however, is largely irrelevant. The focus of our celebration is to commemorate the cosmic event that occurred in Bethlehem over two thousand years ago: God has taken on flesh and become Emmanuel, “God with us.”