
Christmas is an annual festival commemorating the birth of Jesus Christ, observed primarily on December 25 as a religious and cultural celebration among billions of people around the world. A liturgical feast central to Christianity, preparation for Christmas begins on the First Sunday of Advent and it is followed by Christmastide, which historically in the West lasts twelve days and culminates on Twelfth Night. Christmas Day is a public holiday in many countries, is celebrated religiously by a majority of Christians, as well as culturally by many non-Christians, and forms an integral part of the holiday season surrounding it.
There are different hypotheses regarding the date of Jesus's birth. In the early fourth century, the church fixed the date as December 25, the date of the winter solstice in the Roman calendar. It is nine months after Annunciation on March 25, also the Roman date of the spring equinox. 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, part of the Eastern Christian Churches celebrate Christmas on December 25 of the older Julian calendar, which currently corresponds to January 7 in the Gregorian calendar. For Christians, believing that God came into the world in the form of man to atone for the sins of humanity rather than knowing Jesus's exact birth date is considered to be the primary purpose of celebrating Christmas.
The English word Christmas is a shortened form of 'Christ's Mass'. The word is recorded as Crīstesmæsse in 1038 and Cristes-messe in 1131. Crīst (genitive Crīstes) is from the Greek Χριστός (Khrīstos, 'Christ'), a translation of the Hebrew מָשִׁיחַ (Māšîaḥ, 'Messiah'), meaning 'anointed'; and mæsse is from the Latin missa, the celebration of the Eucharist.
The form Christenmas was also used during some periods, but is now considered archaic and dialectal. The term derives from Middle English Cristenmasse, meaning 'Christian mass'. Xmas is an abbreviation of Christmas found particularly in print, based on the initial letter chi (Χ) in the Greek Χριστός (Christ), although some style guides discourage its use. This abbreviation has precedent in Middle English Χρ̄es masse (where Χρ̄ is another abbreviation of the Greek word).
Christmas lights (also known as fairy lights, festive lights or string lights) are lights often used for decoration in celebration of Christmas, often on display throughout the Christmas season including Advent and Christmastide. The custom goes back to when Christmas trees were decorated with candles, which symbolized Christ being the light of the world. The Christmas trees were brought by Christians into their homes in early modern Germany.
In many countries, Christmas lights, as well as other Christmas decorations, are traditionally erected on or around the first day of Advent. In the Western Christian world, the two traditional days when Christmas lights are removed are Twelfth Night and Candlemas, the latter of which ends the Christmas-Epiphany season in some denominations. Taking down Christmas decorations before Twelfth Night, as well as leaving the decorations up beyond Candlemas is historically considered to be inauspicious.