[3] For Christian denominations such as the Anglican Communion or the Lutheran Church, the Twelve Days are identical to Christmastide (December 25 through January 5).

[4][5][6] For the Roman Catholic Church, however, Christmastide lasts longer, running through the Feast of the Baptism of the Lord.

In 567, the Council of Tours "proclaimed the twelve days from Christmas to Epiphany (that is, through the end of 5 January, as Epiphany begins the following day) as a sacred and festive season, and established the duty of Advent fasting in preparation for the feast.

For the Eastern Orthodox, both Christmas and Epiphany are among the Twelve Great Feasts that are only second to Easter in importance.

The Saturday following the Nativity is commemorated by special readings from the Epistle (1 Tim 6:11–16) and Gospel (Matt 12:15–21) during the Divine Liturgy.

The Sunday after the Nativity has its own liturgical commemoration in honour of "The Righteous Ones: Joseph the Betrothed, David the King and James the Brother of the Lord".

The Eve of the Theophany on 5 January is a day of strict fasting, on which the devout will not eat anything until the first star is seen at night.

27 December is the Feast of Saint John the Evangelist, while the 28 December is Childermass or the Feast of the Holy Innocents, in observance of the Massacre of the Innocents of the Nativity narrative, in which Herod the Great, king of Judea, orders the execution of all male children who are two years old and under in the vicinity of Bethlehem.

The transition that evening to the new year is an occasion for secular festivities in many nations, and in several languages is known as "St. Sylvester Night" ("Notte di San Silvestro" in Italian, "Silvesternacht" in German, "Réveillon de la Saint-Sylvestre" in French, and "סילבסטר" in Hebrew).

Several Christian traditions, such as Catholic, Lutheran, Anglican, Methodist, and Moravian churches, offer various forms of Watchnight services, where the congregants are encouraged to review the year passed and pray for the year to come, often in connection with the celebration of Mass or the Lord's Supper.

[22] Some of these traditions were adapted from the older pagan customs, including the Roman Saturnalia and the Germanic Yuletide.

[specify] Some early English colonists brought their version of the Twelve Days with them to North America, and adapted them to their new country, adding their own variations over the years.

In New England, however, both the Pilgrims in Plymouth Colony and the Puritans in Massachusetts Bay frowned upon the observance of Christmas.

Victorian era stories by Charles Dickens, and others, particularly A Christmas Carol, hold key elements of the celebrations such as the consumption of plum pudding, roasted goose and wassail.

[30] In the United States, Christmas Day is a federal holiday which holds additional religious significance for Christians.

Contributing factors include the popularity of the stories of Charles Dickens in nineteenth-century America, with their emphasis on generous giving; introduction of secular traditions in the 19th and 20th centuries, e. g., the American Santa Claus; and increase in the popularity of secular New Year's Eve parties.

In Anglicanism, the designation of the "Twelve Days of Christmas" is used liturgically in the Episcopal Church in the US, having its own invitatory antiphon in the Book of Common Prayer for Matins.