It is the first celebration in the liturgical "Christian Year."
The Christian Year was designed to bring balance to Bible education.
Its adoption by the liturgical churches (emphasis on form and symbolics)
followed a pattern set in the Jewish Synagogue (i.e. Passover, The Day of
Atonement, The Feast of the Pentecost, etc.).
The celebration of the birth of Christ did not become a general part of
Christian tradition until the 4th century. Before that, the Eastern Church
observed the Feast of the Nativity on January 6th.
Between the 4th and the 6th centuries a deep controversy between the
Eastern and Western Churches clouded the teaching of Christ's diety. The
Western Church practiced the celebration of the nativity on December 25th.
Both traditions of the Christian Church determined to emphasize Christ's
incarnation through a formal nativity observance.
The myths of December 25th
It is unlikely that the tradition of celebrating Christ's birthday on
December 25th accurately marks His correct birthday.
The date of December 25th could mark the Christian appropriation
of the Roman "Birthday of the Invincible Sun," instituted in 1274
by the Roman Emperor Aurelian. Later, Emperor Constantine, a believer,
might have borrowed this date to institute a Christian celebration in place
of the pagan one.
Or, December 25th may have been assigned as Christ's birthdate because
it is nine months after March 25th, historically celebrated as the
angelic visitation to the Virgin Mary. Sources from the 4th century support
this.
The coincidence that December 25th also matches the traditional date
of the winter solstice likely influenced the popularity of Christmas,
and the manner of its celebration.
The meaning of Christmas.
Originally the giving of gifts was a pagan custom marking the closing of
the year. Early Christians re-interpreted the practice as a commemoration of
God's greatest gift,
Jesus Christ.
New England Puritans outlawed the celebration of Christmas as "popish
idolatry" in the Massachusetts General Court in 1659. They repealed that law
in 1681.
Since the mid-nineteenth century the celebration has steadily increased
in popularity. Most traditional customs with which we are familiar are of
German and Scandinavian origin.
The Revolutionary War Hessians brought trees into their barracks and
decorated them with ornaments and candles.
The word "Christmas" is derived from the Roman Church's practice of
celebrating the "Mass" (feast) of the Nativity (Christ + Mass = Christmas).
Xmas is not a careless abbreviation of Christmas. Rather, it is a Roman
way of writing the Greek letter "chi," the first letter in the spelling of
"Christos." Xmas is a Christograph.
Santa Claus was actually a sainted Scandinavian priest named "Sint
Nikolaas," (or "Sinterklass") who took it as his mission to provide for the
needs of children.
This year, start a Christmas tradition of being an agent of cheer.
Wise men still seek Him.
Jesus is the reason for the season. 
