Those of us who daily celebrate the Liturgy of the Hours could probably tell that it is getting close to Christmas even if we couldn’t get a look at the calendar, because beginning last Wednesday and continuing through Tuesday evening, December 23rd, before reciting the Magnificat (i.e. “my soul magnifies the Lord”) from Luke 1:46-55, we recite a series of seven ancient antiphons, one each night, which center on the ancient titles of the Messiah. These antiphons have come to be called “the ‘O’ Antiphons” because they begin with “O” in a very literal way. Because they are only said during Advent, they have become ingrained not only in the cycle of the Divine Office itself for this time of the year, they’ve become a part of Advent tradition for many people through the great hymn “O Come O Come Emmanuel,” which is based on the “O Antiphons.”
Father Christian Mathis did a wonderful series on each of the “O Antiphons” back in the early days of Life At 25. The Antiphons for each day are:
December 17th: O Wisdom (O Sapientia) who came from the mouth of the Most High, reaching from end to end and ordering all things mightily and sweetly: come, and teach us the way of prudence.
December 18th: O Lord (O Adonai) and Ruler the house of Israel, who appeared to Moses in the flame of the burning bush and gave him the law on Sinai: come, and redeem us with outstretched arms.
December 19th: O Root of Jesse (O Radix Jesse), that stands for an ensign of the people, before whom the kings keep silence and unto whom the Gentiles shall make supplication: come, to deliver us, and tarry not.
December 20th: O Key of David (O Clavis David), and scepter of the house of Israel, who opens and no man shuts, who shuts and no man opens: come, and lead forth the captive who sits in the shadows from his prison.
December 21st: O dawn of the east (O Oriens), brightness of light eternal, and sun of justice: come, and enlighten those who sit in darkness and in the shadow of death.
December 22nd: : O King of the nations (O Rex gentium) and their desired One, the cornerstone that makes both one: come, and deliver man, whom you formed out of the dust of the earth.
December 23rd: O Emmanuel, God with us, our King and lawgiver, the expected of the nations and their Savior: come to save us, O Lord our God.
All of the “O” invocations are titles of the coming Messiah, and reciting the “O Antiphons” can help us to prepare spiritually for Christmas, since these titles of the Messiah are recited one each day until the 23rd. Vespers (i.e. Evening Prayer) for December 24th actually comprise the first prayers of Christmas itself, and the liturgical season itself changes.
In addition to Father Christian’s series, which I linked to above, Catholic Online has an exceptional series on the “O Antiphons” which I highly recommend. I do have to give credit to Father Adam Kane for the title of this post, it was he who declared it “O time” on his Facebook page back on the 17th. May the Lord richly bless you in these closing days of Advent.