Christmas (Old English: Crīstesmæsse, meaning "Christ's Mass") is an annual commemoration of the birth of Jesus Christ， and a widely observed holiday, celebrated generally on December 25，by millions of people around the world.A feast central to the Christian liturgical year, it closes the Advent season and initiates the twelve days of Christmastide, which ends after the twelfth night.Christmas is a civil holiday in many of the world's nations, is celebrated by an increasing number of non-Christians, and is an integral part of the Christmas and holiday season.
While the birth year of Jesus is estimated among modern historians to have been between 7 and 2 BC, the exact month and day of his birth are unknown. His birth is mentioned in two of the four canonical gospels. By the early-to-mid 4th century, the Western Christian Church had placed Christmas on December 25,a date later adopted in the East.The date of Christmas may have initially been chosen to correspond with the day exactly nine months after early Christians believed Jesus to have been conceived, and became generally associated with the southern solstice (i.e., the Roman winter solstice), with a sun connection being possible because Christians consider Jesus to be the "Sun of righteousness" prophesied in Malachi .
The original date of the celebration in Eastern Christianity was January 6, in connection with Epiphany, and that is still the date of the celebration for the Armenian Apostolic Church and in Armenia, where it is a public holiday. As of 2013, there is a difference of 13 days between the modern Gregorian calendar and the older Julian calendar. Those who continue to use the Julian calendar or its equivalents thus celebrate December 25 and January 6, which on the Gregorian calendar translate as January 7 and January 19. For this reason, Ethiopia, Russia, Georgia, Ukraine, Serbia, the Republic of Macedonia, and the Republic of Moldova celebrate Christmas on what in the Gregorian calendar is January 7.