One of the favorite Christian arguments for the existence of the historical Jesus is the hard data in the gospels: that his birth was in the reign of Herod and of such-and-such a governor of Syria.

Problem is, from the historical evidence we have at hand, those two guys' terms of office seem not to have overlapped. 4 B.C.E., which is usually given as the year of birth [and which itself mocks the year-counting system based on it] is a compromise estimate, not a firm date.