As far as the winter solstice and Christmas, there is no date given in scripture for the birth of Christ it may have actually been spring,
early church leaders decided to celebrate it when they did to stamp out other pagan celebrations at the time.
Since the
early church had no set «canon of Scripture» (we'll deal with this later), no universally accepted doctrinal statements or creeds, no seminaries to teach «correct doctrine», and no Pope or Denominational
leaders to
decide between disagreeing factions, there was a lot of disagreement in the
early church about what was truth and what was «heresy.»