The following is an excerpt from The Winter Pascha , by Fr. Thomas Hopko
Originally there was but one festival in the Christian Church for the Lord's appearing. It was called the "festival of lights" and it was connected both to the Jewish festival of the season, as well as to the pagan celebration which took place at the time of year when the sun stopped its southern march and began to move again towards the north, symbolizing the victory of light over darkness in the natural order. This feast for the Christians was the feast of Epiphany, which literally means "appearing" or "manifestation," also called Theophany, which literally means the appearance or manifestation of God, and was kept on January 6.1 It was given this name, obviously, because God appeared on earth in the person of His Son, and manifested His glory in Him who called Himself the "light of the world."
The separate celebration of Jesus' Nativity apart from the one general celebration of His appearance on earth-- which originally included all aspects of His coming, from His birth to His public manifestation at His baptism in the river Jordan-- was consciously done by the Christian Church, first in the West and later in the East, to offset the pagan holiday of the "Nativity of the Invincible Sun." This pagan festival was celebrated on the twenty-fifth of December. It was a day of religious observance for those who worshipped the heavenly bodies, particularly the sun, as gods. When pagan were liberated from this worship and were blessed to adore the true God as Christians, it was only natural that the Church would replace the erroneous festival with the true one, thus giving genuine significance to a day which was already special in the life of many of its new members. It appears that the main hymn of the feast of Christ's Nativity in the Eastern Church was formulated as a conscious polemic against paganism, with a very pointed flaunting of the fact that those who formerly worshipped the stars, including the sun, were taught by a star to worship the True Sun, God's Son Jesus, who gives, and is, the True Light.
Your Nativity, O Christ our God,
Has shown to the world the light of wisdom
For by it those who worshipped the stars
Were taught by a star to adore You,
The Sun of Righteousness,
And to know You, the Orient from on high.
O Lord, glory to You!
Some people fault the Christian Church for establishing the feast of Christ's birth on the day of the "birth of the sun." Certain Christian sects even oppose the celebration. Orthodox Christians believe that it was an act inspired by the Holy Spirit. God has sent His Son into the world for its sanctification and salvation. The Messiah has com "not to condemn the world," with its feeble and misguided attempts to find life's meaning, "but that the world might be saved through Him" (Jn 3:17). For, as the apostle Paul has written, "it is the God who said 'Let light shine out of darkness,' who has shone in our hearts to give the light of the knowledge of the glory of God in the face [literally person] of Christ" (2 Cor 4:6).
The Magi who had been led on their way by a divine star
Stood before You in wonder at Your marvelous birth;
And bearing gifts, they see the sun
Who rose form the Virgin cloud.
Let the people who sat in darkness
See shining forth the Light that knows no evening,
Him whom the star once manifested
To the fire-worshipping Persian kings.
You have shone forth from a Virgin,
O Spiritual Son of Righteousness,
And a star revealed You,
Whom nothing can contain,
Contained within a cave.
You have led the Magi to worship You,
And joining with them we magnify You.
O Giver of Life, glory to You.
Our savior, the Dayspring from the East,
has visited us from on high;
And we who were in darkness and shadow
Have found the Truth.
For the Lord is born of a Virgin!
1The Armenian Church to this day celebrates but one festival of the Lord's coming, on January 6. This should not be confused with the celebration of Christ's Nativity on January 7 by some Orthodox Churches, for example those in the USSR, which is December 25 according to the Julian calendar which these churches still use.