Christmas or Christmas Day (Old English: Crīstesmæsse, meaning "Christ's Mass") is an annual festival commemorating the birth of Jesus Christ,[7][8] observed most commonly on December 25[4][9][10] as a religious and cultural celebration among billions of people around the world.[2][11][12] A feast central to the Christian liturgical year, it is prepared for by the season of Advent or the Nativity Fast and initiates the season of Christmastide, which historically in the West lasts twelve days and culminates on Twelfth Night;[13] in some traditions, Christmastide includes an Octave.[14] The traditional Christmas narrative, the Nativity of Jesus, delineated in the New Testament says that Jesus was born in Bethlehem, in accordance with messianic prophecies;[15] when Joseph and Mary arrived in the city, the inn had no room and so they were offered a stable where the Christ Child was soon born, with angels proclaiming this news to shepherds who then disseminated the message furthermore.[16] Christmas Day is a public holiday in many of the world's nations,[17][18][19] is celebrated religiously by the vast majority of Christians,[20] as well as culturally by a number of non-Christian people,[1][21][22] and is an integral part of the holiday season, while some Christian groups reject the celebration. In several countries, celebrating Christmas Eve on December 24 has the main focus rather than December 25, with gift-giving and sharing a traditional meal with the family.

Although the month and date of Jesus' birth are unknown, by the early-to-mid fourth century the Western Christian Church had placed Christmas on December 25,[23] a date that was later adopted in the East.[24][25] Today, most Christians celebrate on December 25 in the Gregorian calendar, which has been adopted almost universally in the civil calendars used in countries throughout the world. However, some Eastern Christian Churches celebrate Christmas on December 25 of the older Julian calendar, which currently corresponds to January 7 in the Gregorian calendar, the day after the Western Christian Church celebrates the Epiphany. This is not a disagreement over the date of Christmas as such, but rather a preference of which calendar should be used to determine the day that is December 25. In the Council of Tours of 567, the Church, with its desire to be universal, "declared the twelve days between Christmas and Epiphany to be one unified festal cycle", thus giving significance to both the Western and Eastern dates of Christmas.[26][27][28][29][30] Moreover, for Christians, the belief that God came into the world in the form of man to atone for the sins of humanity, rather than the exact birth date, is considered to be the primary purpose in celebrating Christmas.[31][32][33][34]

Although it is not known why December 25 became a date of celebration, there are several factors that may have influenced the choice. December 25 was the date the Romans marked as the winter solstice,[35] the shortest, and therefore darkest day of the year. Jesus was identified with the Sun based on an Old Testament verse.[36] The date is exactly nine months following Annunciation, when the conception of Jesus is celebrated.[37][38] Finally, the Romans had a series of pagan festivals near the end of the year, so Christmas may have been scheduled at this time to appropriate, or compete with, one or more of these festivals.[39][40][41] Other scholars disagree with this claim and state that the Roman Emperor Aurelian placed a pagan celebration on December 25 in order to compete with the growing rate of the Christian Church, which had already been celebrating Christmas on that date.[42]

The celebratory customs associated in various countries with Christmas have a mix of pre-Christian, Christian, and secular themes and origins.[43] Popular modern customs of the holiday include gift giving, completing an Advent calendar or Advent wreath, Christmas music and caroling, lighting a Christingle, viewing a Nativity play, an exchange of Christmas cards, church services, a special meal, and the display of various Christmas decorations, including Christmas trees, Christmas lights, nativity scenes, garlands, wreaths, mistletoe, and holly. In addition, several closely related and often interchangeable figures, known as Santa Claus, Father Christmas, Saint Nicholas, and Christkind, are associated with bringing gifts to children during the Christmas season and have their own body of traditions and lore.[44] Because gift-giving and many other aspects of the Christmas festival involve heightened economic activity, the holiday has become a significant event and a key sales period for retailers and businesses. The economic impact of Christmas has grown steadily over the past few centuries in many regions of the world.