From Christmas to Easter, every Sunday

At Christmas Day Mass I can't help but be struck as was T.S. Eliot's Thomas Beckett in Murder in the Cathedral:

whenever Mass is said, we re-enact the Passion and Death of Our Lord; and on this Christmas Day we do this in celebration of His Birth. So that at the same moment we rejoice in His coming for the salvation of men, and offer again to God His Body and Blood in sacrifice, oblation and satisfaction for the sins of the whole world. It was in this same night that has just passed, that a multitude of the heavenly host appeared before the shepherds at Bethlehem, saying, 'Glory to God in the highest, and on earth peace, good will toward men'; at this same time of all the year that we celebrate at once the Birth of Our Lord and His Passion and Death upon the Cross.

Eliot has Beckett remark to his flock, "Beloved, as the World sees, this is to behave in a strange fashion." But indeed, this is what the Church does every Sunday.

The Gloria in excelsis, called "a most ancient and venerable hymn by which the Church, gathered in the Holy Spirit, glorifies and entreats God the Father and the Lamb" in the General Instruction of the Roman Missal, occurs in the entrance rites of every Sunday Mass. Its opening clauses,

Gloria in excelsis Deo
et in terra pax hominibus bonae voluntatis,

are of course the declaration of the angels before the shepherds, which Eliot has Beckett cite from Luke 2:14 (it can also be "peace to men of good will," depending on your translation). Commencing its worship with this phrase, the Church is already doing what it later declares expressly, "joining with angels and archangels and all the company of heaven," with which words the Mass proceeds to declare

Sanctus, Sanctus, Sanctus
Dominus Deus Sabaoth.
Pleni sunt caeli et terra gloria tua.
Hosanna in excelsis.

The Sanctus comes as the final words of the preface for the Eucharistic prayer. That is: the Mass identifies the Church with the angelic choir, implicitly at its beginning, and again explicitly at the beginning of the Eucharist proper. There is thus a sense in which the Church is, with every Mass, recapitulating the distance and the conjunction between Christmas and Holy Week; and this sense is in some wise bound up with its angelic vocation.