Christmas or Christmas Day (Old English: Crīstesmæsse, literally "Christ's mass") is an annual commemoration of the birth of Jesus Christ,^[5][6] celebrated generally on December 25^[2][3][4] as a religious and cultural holiday by billions 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.^[7] Christmas is a civil holiday in many of the world's nations,^[8][9][10] is celebrated by an increasing number of non-Christians,^[1][11][12] and is an integral part of the Christmas and holiday season.

The precise year of Jesus' birth, which some historians place between 7 and 2 BC, is unknown.^[13][14] By the early-to-mid 4th century, Western Christianity had placed Christmas on December 25, a date later adopted in the East.^[15][16] The date of Christmas may have initially been chosen to correspond with the day exactly nine months after the Annunciation, the date Christians believe Jesus to have been conceived,^[17] as well as the date of 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 4:2.^{[17][18][19][20][21]}

Epiphany (Koine Greek: ἐπιφάνεια, epiphaneia, "manifestation", "striking appearance"^[1]) or Theophany^[2] (Ancient Greek (ἡ) Θεοφάνεια, Τheophaneia meaning "vision of God"^[3]), which traditionally falls on 6 January, is a Christian feast day that celebrates the revelation of God the Son as a human being in Jesus Christ. Western Christians commemorate principally (but not solely) the visitation of the Biblical Magi to the Baby Jesus, and thus Jesus' physical manifestation to the Gentiles. Eastern Christians commemorate the baptism of Jesus in the Jordan River, seen as his manifestation to the world as the Son of God.^[4]

Eastern Churches following the Julian Calendar observe the Theophany feast on what for most countries is 19 January^[5] because of the 13-day difference today between that calendar and the generally used Gregorian calendar.^[6]