Christmastide (also Christmas or the Christmas season) is one of the seasons of the liturgical year of most Christian churches. It tends to be defined (with slight variations) as the period from Christmas Eve to the Epiphany. This period is also commonly known as the Twelve Days of Christmas, as referred to in the Christmas carol of the same name, or Yuletide, as in “Deck the Halls.”

Many Protestant churches add an Epiphany season after the Christmas season, extending the celebration of Christmas for forty days until the feast of the Presentation of Christ in the Temple (Candlemas) on 2 February (or a nearby Sunday). In the Missal and Breviary of the Roman rite, since 1970, the Christmas season runs a shorter period, from Christmas Eve to the Baptism of the Lord,  which depending on the place and the year can occur between 7 January and 13 January. In the Little Office of the Blessed Virgin Mary,  the season runs from Vespers on 24 December till Compline  on 2 February.

During the season, various festivities are traditionally enjoyed and buildings decorated. In some countries the superstition has arisen that it is bad luck to leave the decorations up after Twelfth Night. 

Advent, anglicized from the Latin word adventus meaning “coming”, is a season observed in many Western Christian churches, a time of expectant waiting and preparation for the celebration of the  Nativity of Jesus at Christmas. It is the beginning of the Western liturgical year and commences on Advent Sunday, called Levavi. The Eastern churches’ equivalent of Advent is called the Nativity Fast, but it differs both in length and observances and does not begin the church year, which starts instead on September 1.

The progression of the season may be marked with an Advent calendar,  a practice introduced by German Lutherans. At least in the Roman Catholic, Anglican, Lutheran, Moravian, Presbyterian, and Methodist calendars, Advent starts on the fourth Sunday before December 25, the Sunday from November 27 to December 3 inclusive.

Latin adventus is the translation of the Greek word parousia, commonly used in reference to the Second Coming of Christ . For Christians, the season of Advent anticipates the coming of Christ from two different perspectives. The season offers the opportunity to share in the ancient longing for the coming of the Messiah, and to be alert for his Second Coming.