Christmas is an annual holiday that celebrates the birth of Jesus. Christmas festivities often combine the commemoration of Jesus' birth with various secular customs, many of which have been influenced by earlier winter festivals.

In most places around the world, Christmas Day is celebrated on December 25. Christmas Eve is the preceding day, December 24. In the United Kingdom and many countries of the Commonwealth, Boxing Day is the following day, December 26. In Catholic countries, Saint Stephen's Day or the Feast of St. Stephen is December 26. The Armenian Apostolic Church observes Christmas on January 6. Eastern Orthodox Churches that still use the Julian Calendar celebrate Christmas on the Julian version of 25 December, which is January 7 on the more widely used Gregorian calendar, because the two calendars are now 13 days apart. (Armenians who use the Julian Calendar celebrate Christmas on the Julian version of Jan. 6, which is Jan. 19 on the Gregorian calendar.) The word "Christmas" is a contraction of two words "Christ's mass" and is derived from the Middle English Christemasse and Old English Cristes mćsse, a phrase first recorded in 1038. In early Greek versions of the New Testament, the letter Śś (chi), is the first letter of Christ (ŚśŚŃŚÉŚŇŚÓός). Since the mid-16th century Śś, or the similar Roman letter X, was used as an abbreviation for Christ. Thus, Xmas is an abbreviation for Christmas. After the conversion of Anglo-Saxons in England from their indigenous Anglo-Saxon polytheism (a form of Germanic paganism) in the very early 7th century, Christmas was called geol, which was the name of the native Germanic pre-Christian solstice festival that fell on that date. From geol, the current English word Yule is derived. Many customs associated with modern Christmas were derived from Germanic paganism. The prominence of Christmas Day increased gradually after Charlemagne was crowned on Christmas Day in 800. Around the 12th century, the remnants of the former Saturnalian traditions of the Romans were transferred to the Twelve Days of Christmas (26 December - 6 January). Christmas during the Middle Ages was a public festival, incorporating ivy, holly, and other evergreens, as well as gift-giving. Modern traditions have come to include the display of Nativity scenes, Holly and Christmas trees, the exchange of gifts and cards, and the arrival of Father Christmas or Santa Claus on Christmas Eve or Christmas morning. Popular Christmas themes include the promotion of goodwill and peace.