Christmas is celebrated on December 25th each year to commemorate the birth of Jesus Christ. It is a religious and cultural holiday celebrated by billions around the world. While the exact date of Jesus' birth is unknown, by the 4th century the Western Christian Church had set the date as December 25th, a tradition that later spread East. Today most Christians celebrate on this Gregorian calendar date, though some Eastern churches use the older Julian calendar which falls on January 7th. The winter solstice and Roman pagan festivals held around the same time may have influenced the early Church's choice of December 25th for Christmas.

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2.  Christmas or Christmas Day is an annual festival
commemorating the birth of Jesus Christ, observed most commonly
on December 25 as a religious and cultural celebration among
billions of people around the world. A feast central to
the Christian liturgical year, it is prepared for by the season
of Advent or the Nativity Fast and initiates the season
of Christmastide, which historically in the West lasts twelve
days and culminates on Twelfth Night: in some traditions,
Christmastide includes an Octave. Christmas Day is a
public holiday in many of the world's nations, is celebrated
culturally by a large number of non-Christian people, and is an
integral part of the holiday season, while some Christian groups
reject the celebration. In several countries, celebrating Christmas
Eve on December 24 has the main focus rather than December 25,
with gift-giving and sharing a traditional meal with the family.

4.  Although the month and date of Jesus' birth are unknown, by the early-to-
mid 4th century the Western Christian Church had placed Christmas on
December 25, a date which was later adopted in the East.
 Today, 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, some Eastern
churches celebrate Christmas on the December 25 of the older Julian
calendar, which currently corresponds to January 7 in the Gregorian
calendar, the day after the Western Christian Church celebrates
the Epiphany. This is not a disagreement over the date of Christmas as
such, but rather a preference of which calendar should be used to
determine the day that is December 25. In the Council of Tours of 567, the
Church "declared the twelve days between Christmas and Epiphany to be
one unified festal cycle", thus giving significance to both December 25 and
January 6.
 Although it is not known why December 25 became a date of celebration,
there are several factors that may have influenced the choice. December 25
was the date the Romans marked as the winter solstice, and Jesus was
identified with the Sun based on an Old Testament verse. The date is
exactly nine months following Annunciation, when the conception of Jesus
is celebrated. Finally, the Romans had a series of pagan festivals near the
end of the year, so Christmas may have been scheduled at this time to
appropriate, or compete with, one or more of these festivals.