Happy Christmas!

Guido Da Siena - Nativity
Source: Wiki .Ccommons.

Wishing everyone a very happy feast of the Nativity and twelve days of Christmas!

Christmas from c860 to the 1963 breviary 

And as you say the Office today, keep in mind that you are saying (or hopefully singing or at least listening to them being sung!) very ancient chants indeed.

Most of the antiphons and responsories at Matins and Lauds can be found in exactly the same positions or in a few cases with a bit of reordering, in the earliest surviving Office books from the ninth century, and almost certainly date back much further than that.

The Lauds hymn, A solis ortus cardine, dates from the fifth century, while the hymn used at Matins and Vespers, Christe Redemptor omnium, dates from the sixth century.

Responsory Descendit de caelis

To give you the flavour of the season, here is a recording of one of the ancient responsories of Christmas, a responsory that appears in the oldest surviving full Benedictine Office book (circa 860 AD) as well as in the 'Old Roman' sources.

In the ancient Benedictine book, it is the last responsory of Matins for the Nativity, and many monasteries retained in that position until quite late indeed.  But in the secular cursus it seems to have been used earlier in the sequence - the contemporary Compiège antiphoner places it at the end of the first Nocturn for example, and the (monastic) Hartker antiphoner a century followed suit, placing it in its current position as the last responsory of the first Nocturn.

The text (trans Lew) is:

R. Descéndit de caelis Deus verus a Patre génitus, † introívit in úterum Vírginis, nobis ut apparéret visíbilis, indútus carne humána protoparénte édita: * Et exívit per portem clausam † Deus et homo, Lux et vita, cónditor mundi. V. Tamquam sponsus † Dóminus procédens de thálamo suo. R. Et exívit per portem clausam † Deus et homo, Lux et vita, cónditor mundi. V. Glória Patri, et Fílio, et Spirítui Sancto. R. Et exívit per portem clausam † Deus et homo, Lux et vita, cónditor mundi.

R. He came down from heaven: true God, begotten of the Father: he entered the Virgin's womb, that he might be made clearly manifest to us, clothed in human flesh put forth by the Creator, * He went out through the closed door, God and man, Light and Life, Author of the world. V. Like a bridegroom, the Lord coming forth from his chamber. R. He went out through the closed door, God and man, Light and Life, Author of the world. V. Glory be to the Father, and to the Son, and to the Holy Ghost. R. He went out through the closed door, God and man, Light and Life, Author of the world.