Before Christianity

There is precious little information about the birth of Christ in the Bible, and no suggestion that birthdays were celebrated in those times. There is no Biblical reason for celebrating the birth of Christ. The Christmas we know started out as a pagan celebration.
The early church seized the opportunity to superimpose Christ's birth on top of the winter solstice observance that was already firmly in place at that time of year (Saturnalia in Ancient Rome) and not likely to be forgotten, thus re-routing non-believers to the new religion.
 In return for the observance of Christ's birth on December 25th laid as a veneer on top of the old observance, the church allowed the old holiday to be celebrated more or less the way it had always been.
Many of our holidays are derived from celebrations that precede the establishment of Christianity or are appropriations by the church to honor Christian themes.
Halloween is often misunderstood as utterly pagan, but is based on All Soul's Day and All Hallowed Eve, which in turn is an appropriation of  an earlier pagan observance. Halloween is not non-Christian.
Devils, witches and ghosts all have specific meanings within a Christian context, which is why the holiday stirs up so much resentment and confusion among fundamentalists. Halloween's cousin, The Day of the Dead, has more Christianity intact, but is likewise  a pagan/Christian hybrid. Valentine's Day, based on the theme of a Christian saint, is another pagan celebration with a Christian overlay.
Easter is a devotional time for many, but is also family centered entertainment with eggs and rabbits which are pagan symbols. In their book "4,000 Years of Christmas" Earl and Alice Count trace the underpinnings of Christmas back to Mesopotamia, the ancient mother of civilization. Despite the original intention of the church in inventing Christmas, there is simply no proof that it is or ever has been a primarily Christian event.
This isn't criticism, in fact paganism has contributed to the broad appeal and flexibility of Christmas as a holiday so multi-faceted that some aspect of it can be observed  by practically everyone. Christmas attracts people from different faiths and of no particular faith because there is a perfect psychological and symbolic fit between it and the time of year.The church's hold over Christmas was and remains rather tenuous. Some of the pre-Christian features surviving within our Christian traditions and symbols today are the lights and candles, the eternal circle of the wreath, wassailing (which became door-to-door caroling) and the evergreens, holly and mistletoe.