In my book: Important Dates in the Lives of Jesus and Mary
I discuss the true historical date for the Birth of Christ. I'll give a quick overview here.
1. Bl. Anne Catherine Emmerich states, from her visions from God, that Jesus was born November 25th, not in December.
2. my research into eschatology supports 15 BC as the year of Christ's birth. There are a number of reasons why the early date is the best fit for the information we have (too lengthy to explain here).
3. The Christmas star was a comet, which broke into pieces, forming a pattern in the sky which the 3 Magi interpreted as the birth of a new king.