Dom Gueranger comments: "...This today is the Day of eternity, a Day which has neither morning nor evening, neither rising nor setting." (The Liturgical Year, Vol. II) Through the sacraments, especially through the Eucharistic sacrifice, we already belong to that Day of eternity. At Christmas Mass, we truly and mystically assist at His birth.
Christmas is celebrated with three Masses. At Midnight Mass, the angels marvel at the Word made flesh, born of the Virgin Mary. The Dawn Mass sees the shepherds hurrying to the stable to adore the newborn King. The third Mass celebrates the Eternal Word, Who is the Son begotten of the Father from all eternity.
Jesus, Who is born tonight, is born thrice. He is born of the Blessed Virgin, in the stable of Bethlehem; he is born by grace, in the hearts of the shepherds, who are the first fruits of the Christian Church; and He is born from all eternity in the bosom of the Father, in the brightness of the saints: to this triple birth, therefore, let there be the homage of a triple Sacrifice! (Dom Gueranger, The Liturgical Year, Vol. II)