Christmas or Christmas Day is a holiday generally observed on December 25 (with alternative days of January 7 for many Orthodox churches, January 6 for the Armenian Apostolic Church and January 19 for the Armenians of Jerusalem and the Holy Land) to commemorate the birth of Jesus, the central figure of Christianity. The date is not known to be the actual birthday of Jesus, and may have initially been chosen to correspond with either the day exactly nine months after Christians believe Jesus to have been conceived, the date of the Roman winter solstice, or one of various ancient winter festivals.Christmas is central to the Christmas and holiday season, and in Christianity marks the beginning of the larger season of Christmastide, which lasts twelve days. Although nominally a Christian holiday, Christmas is also celebrated by an increasing number of non-Christians worldwide, and many of its popular celebratory customs have pre-Christian or secular themes and origins. Popular modern customs of the holiday include gift-giving, music, an exchange of Christmas cards, church celebrations, a special meal, and the display of various decorations; including Christmas trees, lights, garlands, mistletoe, nativity scenes, and holly. In addition, in Western Christianity several figures, known as Saint Nicholas, Father Christmas, and Santa Claus, among other names, are associated with bringing gifts to children during the Christmas season.

The Christmas tree, also known as a Yule tree, is a decorated evergreen coniferous tree, real or artificial, and a tradition associated with the celebration of Christmas. The tradition of decorating an evergreen tree at Christmas started in Livonia and Germany in the 16th century.The Christmas tree is traditionally brought into the home and decorated with Christmas lights (originally candles), ornaments, garlands, tinsel, and candy canes during the days around Christmas. An angel or star is placed at the top of the tree, representing the host of angels or the Star of Bethlehem from the Nativity.

The first specifically Christmas hymns that we know of appear in 4th century Rome. Latin hymns such as Veni redemptor gentium, written by Ambrose, Archbishop of Milan, were austere statements of the theological doctrine of the Incarnation in opposition to Arianism. Corde natus ex Parentis (Of the Father's love begotten) by the Spanish poet Prudentius is still sung in some churches today. In the 9th and 10th centuries, the Christmas "Sequence" or "Prose" was introduced in North European monasteries, developing under Bernard of Clairvaux into a sequence of rhymed stanzas. In the 12th century the Parisian monk Adam of St. Victor began to derive music from popular songs, introducing something closer to the traditional Christmas carol.

Christmas is typically the largest annual economic stimulus for many nations around the world. Sales increase dramatically in almost all retail areas and shops introduce new products as people purchase gifts, decorations, and supplies. In the U.S., the "Christmas shopping season" starts as early as October.In Canada, merchants begin advertising campaigns just before Halloween (October 31), and step up their marketing following Remembrance Day on November 11. In the UK and Ireland, the Christmas shopping season starts from mid November, around the time when high street Christmas lights are turned on.In the United States, it has been calculated that a quarter of all personal spending takes place during the Christmas/holiday shopping season.[118] Figures from the U.S. Census Bureau reveal that expenditure in department stores nationwide rose from $20.8 billion in November 2004 to $31.9 billion in December 2004, an increase of 54 percent. In other sectors, the pre-Christmas increase in spending was even greater, there being a November – December buying surge of 100 percent in bookstores and 170 percent in jewelry stores. In the same year employment in American retail stores rose from 1.6 million to 1.8 million in the two months leading up to Christmas.Industries completely dependent on Christmas include Christmas cards, of which 1.9 billion are sent in the United States each year, and live Christmas Trees, of which 20.8 million were cut in the USA in 2002.In the UK in 2010, up to £8 billion was expected to be spent online at Christmas, approximately a quarter of total retail festive sales. Economic

Santa Claus, or "Santa", is a figure in North American culture which developed from an amalgamation of Dutch Sinterklaas, English Father Christmas and other traditions of Christmas gift-bringers. Santa Claus is said to bring gifts to the homes of the good children during the late evening and overnight hours of Christmas Eve, December 24. The figure developed in the 19th century from the Dutch figure of Sinterklaas,which, in turn, may have part of its basis in hagiographical tales concerning the historical figure of gift giver Saint Nicholas. Santa Claus is generally depicted as a plump, jolly, white-bearded man wearing a red coat with white collar and cuffs, white- cuffed red trousers, and black leather belt and boots (images of him rarely have a beard with no moustache). This image became popular in the United States and Canada in the 19th century due to the significant influence of caricaturist and political cartoonist Thomas Nast.This image has been maintained and reinforced through song, radio, television, children's books and films. The North American depiction of Santa Claus as it developed in the 19th and 20th century in turn influenced the modern perceptions of Father Christmas, Sinterklaas and Saint Nicholas in European culture.