Because Christianity and the New Testament came into existence during the early years of the Roman Empire, New Testament writers often refer to well-known figures from the history of imperial Rome. For example, when the evangelist Matthew tells his well-known version of the birth of Jesus, he mentions two kings of Roman-ruled Judea who only held power with the permission of Caesar Augustus. These two rulers were Herod the Great and his son and successor Archelaus. As the familiar story in the second chapter of Matthew tells it, Joseph fled into Egypt with his family to escape Herod's infamous Slaughter of the Innocents. He remained in Egypt until he had learned that Herod was dead:But when he heard that Archelaus reigned over Judea in place of his father Herod, Joseph was afraid to go there, and being warned in a dream he withdrew to the district of Galilee. (Matthew 2:22)When Luke tells his even more famous version of the Nativity story, he begins his account with references to two Romans:In those days a decree went out from Caesar Augustus that all the world should be enrolled. This was the first enrollment, when Quirinius was governor of Syria. (Luke 2:1-2)All four of the personages just mentioned are important enough to imperial Roman history that we know numerous factual details about them. From information found in old books and from statues and inscriptions, we can locate trustworthy dates for many of the events in the lives of these well-known persons:1. Caesar Augustus was born in September of 63 B.C., became the first Roman emperor in 27 B.C. at the age of 36, and died in 14 A.D.If you glance through these dates casually, they seem to be roughly consistent with the stories told by Matthew and by Luke; if you look more carefully, however, there is a glaring inconsistency. On the one hand, Matthew says that Jesus was born during the reign of Herod the Great, that is, sometime before Herod's death in 4 B.C. On the other hand, Luke says that Jesus was born when Quirinius was governor of Syria, that is sometime between 6 A.D. and 12 A.D. In other words, Matthew's story has Jesus being born around 6 or 7 B.C. while Luke's account has the Nativity occurring around 6 or 7 A.D. or even later. Simple arithmetic shows that the two gospel accounts disagree by 12 or 14 years, possibly by even more.
2. Publius Sulpicius Quirinius was born in 51 B.C., served as governor of the Roman province of Syria from 6 A.D. to 12 A.D., and died in 21 A.D.
3. Herod the Great was born in 73 B.C. and died in 4 B.C.
4. Archelaus succeeded Herod the Great in 4 B.C. but was removed from the throne by order of Augustus in 6 A.D.
I am by no means the first person to notice this inconsistency. Google the key words "birth of Jesus" or "chronology of Jesus" and you will find hundreds of entries which discuss this inconsistency. Read through these discussions of the dating problem and you will find that professional Bible scholars have never reached widespread agreement on the significance of the inconsistent dates in Matthew and Luke. However, the centuries-old idea that the Bible is inerrant, i.e., without errors, and that it is the divinely inspired revelation from God -- that traditional view held so dear by fundamentalist Christians is challenged by the discovery of such inconsistencies. It is perfectly clear that someone somewhere has clearly got the Nativity dates wrong. With all due respect to those who believe in the literal inerrancy of a divinely-inspired Bible, the Bibles we purchase at Christian book stores and those we find in the pews of our churches have at least one widely recognized error in them.
Perhaps Luke simply got some of his facts wrong; perhaps someone copying Luke's original manuscript inserted an inaccurate comment; perhaps there is as yet undiscovered material that will resolve what is really only an apparent inconsistency; perhaps the Bible as we know it today is a somewhat garbled version of what God inspired Luke and Matthew to write; perhaps, perhaps, perhaps! As I said earlier, there are hundreds of opinions on this matter. So what follows below are a few comments and opinions that seem sensible to me.
I. Historiography -- How History Gets Written
Since Matthew and Luke are both narratives of past events that supposedly really happened, they are rightly considered as part of the genre we call history. Calling these two gospels histories, however, can be very misleading because what the historians of different eras have considered proper historical writing has produced a very broad spectrum of approaches to history. The study of these different approaches is called historiography. It is a course that master's degree and PH.D. candidates in history are almost always required to take. That means that the odds against the typical American college graduate knowing anything about historiography are about 1000 to 1. In a university with 15,000 students there will seldom be more than 15 graduate students in history.
Without over-simplifying too much, historiographers study the motives, materials, techniques, and standards of evidence which guide various historians from the past and the present.