A Pharisee whose name was Gamaliel, a teacher of the law who was respected by all the people, stood up in the council and ordered the men to be put outside for a short time. 5:35 Then he said to the council, “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.

This account of Theudas appears to be somewhat at odds with Josephus’ account of an episode involving a man of the same name.

Luke records Gamaliel as stating that the revolt of Judas the Galilean took place after that of Theudas.  But Josephus places Theudas in the governorship of Fadus (44-46 AD).  This would have about a decade after the incident recorded here by Luke.  Judas the Galilean, on the other hand, rose up around 6 AD, according to Josephus.

It has been pointed out that since Josephus describes four different men names Simon and three named Judas within a few years (all of whom instigated rebellions), he and Luke may actually be referring to different individuals.

As Peterson states, it is unlikely that Luke (and, we might add, impossible that Gamaliel) has misread Josephus, since his work was not published until about AD 93.  It is probable (says Peterson) that Gamaliel is referring to a different Theudas.

Alternatively (since Josephus is know to have made a number of historical errors, and Luke is a demonstrably accurate historian), we might opt for Luke’s account rather than that of Josephus as being correct.  Yet another option might be allow that Luke (or Gamaliel himself!) might have made a (trivial) error here (this is the suggestion of I.H. Marshall, in his book Inspiration; he cites this passage in support of his contention that Scripture is best described as ‘infallible’, rather than ‘inerrant’).

Calvin thought that the words here translated ‘after that’ meant ‘over and above’ or ‘besides’.

Keener writes that ‘Theudas is not a common enough name to make an earlier revolutionary named Theudas likely, although the name does occur (e.g., in a Jerusalem tomb inscription). Luke may simply fill in names of the most prominent revolutionary leaders known by his own period rather than a less-known name Gamaliel might have cited (historians sometimes adjusted characters’ speeches in their own words); the alternative would be that either Luke or Josephus is mistaken.’ (IVPBBC)

Barrett thinks that it is possible, but not probable, that the present account is historically accurate.  He writes that the ‘simple solution’ would be to say ‘that Luke, writing Gamaliel’s speech (for the Christians can hardly have had inside information of what was said in the Sanhedrin after v. 34—unless Gamaliel’s pupil, Saul of Tarsus, was present!), made a mistake, either unaware of the true date of Theudas or confusing him with some other rebel.’

My own instinct is to side with the historical accuracy of Luke’s account, but I cannot be certain about this.