"At the Office of Prime, in cathedral chapters and monasteries, the announcement of tomorrow's feast is made with unusual solemnity. The lector, who frequently is one of the dignitaries of the choir, sings, to a magnificent chant, the following lesson from the Martyrology. All the assistants remain standing during it, until the lector comes to the word Bethlehem, at which all genuflect, and continue in that posture until all the glad tidings are told."
The Liturgical Year, Dom Gueranger
Octavo Kalendas Januarii
Anno a creatione mundi, quando in principio Deus creavit
caelum et terram, quinquies millesimo centesimo nonagesimo nono; a diluvio vero, anno bis millesimo nongentesimo quinquagesimo septimo; a nativitate Abrahae,
anno bis millesimo quintodecimo; a Moyse et egressu populi Israel de Aegypto,
anno millesimo quingentesimo decimo; ab unctione David in regem, anno millesimo
trigesimo secundo; Hebdomada sexagesima quinta, juxta Danielis prophetiam;
Olympiade centesima nonagesima quarta; ab urbe Roma condita, anno
septingentesimo quinquagesimo secundo; anno Imperii Octaviani Augusti
quadragesimo secundo; toto Orbe in pace composito, sexta mundi aetate,
Jesus Christus, aeternus Deus aeternique Patris Filius, mundum volens adventu
suo piissimo consecrare, de Spiritu Sancto conceptus, novemque post conceptionem
decursis mensibus, in Bethlehem Judae nascitur ex Maria Virgine factus homo: NATIVITAS DOMINI NOSTRI JESU CHRISTI SECUNDUM
CARNEM!