The beginning of Luke 2 presents one of the best-known challenges to the historicity of the Gospel narratives:

2:1 Now in those days a decree went out from Caesar Augustus to register all the empire for taxes. 2:2 This was the first registration, taken when Quirinius was governor of Syria.

I have explored the problem, and its possible solutions, in some detail elsewhere.

To be brief, the problem is that the census associated with Quirinius is usually dated to around 6AD, whereas the birth of Jesus took place about 8 years earlier.

I incline to the theory that Luke means that the ‘registration’ which brought Joseph and the pregnant Mary from Nazareth to Bethlehem occurred before the registration associated with Quirinius.

But why would Luke even mention a registration/census that took place some years after the birth of Jesus?

Well, it might be because the Quirinius registration was particularly memorable.

Enter Acts 5:37, which has Gamaliel saying:

Acts 5:35 “Men of Israel, pay close attention to what you are about to do to these men. 5:36 For some time ago Theudas rose up, claiming to be somebody, and about four hundred men joined him. He was killed, and all who followed him were dispersed and nothing came of it. 5:37 After him Judas the Galilean arose in the days of the census, and incited people to follow him in revolt. He too was killed, and all who followed him were scattered.”

Scholars are pretty much agreed that this refers to the census of Quirinius in AD6.  But note the simple reference: ‘the census’.  This suggests that it was a major event, one that had lodged itself in the mind of the people for many years (this even recorded in Acts took place around 30 years later).  This fact itself would help to explain why Luke (in his Gospel, chapter 2) might refer to the census that brought Joseph and Mary from Nazareth to Bethlehem as occuring before this better-known census.

Jason Engwer adds that this later census clearly took place in turbulent times.  No such turbulance is apparent in Luke 2 –

‘Mary, Joseph, the shepherds, etc. interact with people, travel, and so on without any mention of the unrest surrounding the 6 A.D. census or any suggestion that the individuals involved in the opening chapters of Luke were concerned about such matters.’

We have, then, some evidence (but not proof) that the census of Luke 2 and that of Acts 5 are separate and equally historical events, or, according to Engwer, part of the same, prolonged, event.