A Real Event

"Now in those days a decree went out from Caesar Augustus, that a census be taken of all the inhabited earth. This was the first census taken while Quirinius was governor of Syria. And everyone was on his way to register for the census, each to his own city. Joseph also went up from Galilee, from the city of Nazareth, to Judea, to the city of David which is called Bethlehem, because he was of the house and family of David, in order to register along with Mary, who was engaged to him, and was with child."

Luke 2:1-5

In order for Rome to know how much money they could collect through taxation, they needed the people of the empire to register. For Joseph and Mary, it meant traveling over 60 miles to Joseph's hometown.  About a three day trip on foot. It was especially hard on Mary, who was very close to delivering her baby. 

Luke gave Theophilus, the man to whom he is writing this account, more details about the Roman government than he did about Joseph and Mary's trip. Why? Bob Deffinbaugh, Pastor of Community Bible Chapel in Richardson Texas writes,"Who cares which Caesar was responsible for the census, or even that there was one? Who cares about Quirinius? In my opinion, Theophilus, the initial recipient did. The term “most excellent,” which Luke uses in chapter 1 (v. 3), is also used by Luke three times in Acts (23:26; 24:3; 26:25), each time in reference to a political official of high standing. This suggests that Theophilus, too, was a man of high political office. Luke’s information, while of little interest to us, must have been significant to Theophilus. Among other things, Luke was showing the historical roots of the Christian faith. Unlike the appearance of the other “gods” of false religions, whose appearance was couched in 'once upon a time' terms, the coming of the Christ was a real event in real time. The facts Luke has provided were important to a man whose faith was to have historical validity." 

The birth of Jesus Christ is not some nice Christmas fairy tale. It has "historical validity".