Today is the eighth day of the twelve days of Christmas. It also marks the end of the Octave, that being the first eight days of Christmas.
In modern times, we celebrate the Solemnity of Mary. This feast was celebrated in Rome on 1 January beginning in the 5th century, but in the 13th century, it was replaced by The Feast of the Circumcision of Christ. In 1974, Pope Paul VI removed the Feast of the Circumcision from the liturgical calendar and reestablished the Feast of Mary on 1 January. Also celebrated on this day, for over a millennium, was the Feast of Fools.
The Solemnity of Mary, Mother of God (Feast Day)
This Feast commemorates the divine motherhood of the Blessed Virgin Mary:
The Solemnity of Mary Mother of God falls exactly one week after Christmas, the end of the octave of Christmas. It is fitting to honor Mary as Mother of Jesus, following the birth of Christ. When Catholics celebrate the Solemnity of Mary Mother of God we are not only honoring Mary, who was chosen among all women throughout history to bear God incarnate, but we are also honoring our Lord, who is fully God and fully human. Calling Mary "mother of God" is the highest honor we can give Mary. Just as Christmas honors Jesus as the "Prince of Peace," the Solemnity of Mary Mother of God honors Mary as the "Queen of Peace" This solemnity, falling on New Year's Day, is also designated the World Day of Peace.
The Feast of the Circumcision of Christ (Historical: 13th - 20th c.)
Jesus was circumcised in obedience to Jewish law (Genesis 17:10-12) on the eighth day following his birth (Luke 2:21). "The circumcision of Jesus has traditionally been seen, as explained in the popular 13th century work the Golden Legend, as the first time the blood of Christ was shed, and thus the beginning of the process of the redemption of man, a demonstration that Christ was fully human, and an act of obedience to Biblical law."
This Feast eventually fell into disfavor. Indeed, Pope Leo XIII, during his papacy at the end of the 19th century, threatened excommunication to anyone who spoke of Jesus's foreskin, and the Feast was banished from the liturgical calendar by Pope Paul VI in 1974. Apparently the only place that the feast is still celebrated openly is in the small Italian town of Calcata where the local Church claims to have possessed the remnant of Christ's circumcision for several centuries.
The Feast of Fools (Historical: 5th - 17th c.)
The Feast of Fools, celebrated from the 5th to the 17th century throughout Europe, was a "celebration marked by much license and buffoonery." It in many ways resembles the pagan Roman celebration of Saturnalia:
In the medieval version the young people, who played the chief parts, chose from among their own number a mock pope, archbishop, bishop, or abbot to reign as Lord of Misrule. Participants would then "consecrate" him with many ridiculous ceremonies in the chief church of the place, giving names such as Archbishop of Dolts, Abbot of Unreason, Boy Bishop, or Pope of Fools. The protagonist could be a boy bishop or subdeacon, while at the Abbey of St Gall in the tenth century, a student each December 13 enacted the part of the abbot. In any case the parody tipped dangerously towards the profane. The ceremonies often mocked the performance of the highest offices of the church, while other persons, dressed in different kinds of masks and disguises, engaged in songs and dances and practised all manner of revelry within the church building.
The Feast of Fools was never a sanctioned feast - and indeed, it was often condemned by the Church - but it was a popular feast. The Feast of Fools was finally forbidden under the very severest penalties by the Council of Basel in 1431, but the festivals didn't die out until 1644, when the last Feast of Fools was celebrated in Paris.
The Feast of Fools figures in at least one major literary work. In "The Hunchback of Notre Dame," Victor Hugo has Quasimodo elected as King of Fools to lead the local celebration.