Historians and biblical scholars have long known that the (different) Birth Narratives in Matthew and Luke (they do not appear in either Mark or John), probably deriving from a common source, were invented to give Jesus a provenance commensurate with his deification. To do so, they borrowed from other contemporary religions where stories like that of the nativity could be found.
All we know of Jesus’ birth is that it must have been in Galilee (all his disciples except Judas were Galilean), probably in Capernaum (‘his own city’, Matt. 9:1), where he preached in the synagogue.
The claim that he was born in Bethlehem derives from a prophecy (Mic. 5:2) that the Messiah would ‘come out of’ that city (that doesn’t necessarily mean that he had to be born there). However, it is telling that there is no record of Jesus claiming to come from either Bethlehem or Nazareth (the sobriquet ‘Nazarene’, by which he was known, has nothing to do with Nazareth). That is probably because he was known to come from Galilee.
So one can forget the Wise Men, the birth in a stable, the Star of Bethlehem and the extraordinary journeys across Palestine. All were invented and borrowed from contemporary beliefs about other saviour gods, especially Mithras, the god of the Roman army. The Mithraic books tell how, when Mithras was born, a star fell from the sky and was followed by Zoroastrian priests called 'Magi' on their way to worship him. This birth was witnessed by shepherds.
Some believe that Jesus was born about 4 BC because of the story of the Massacre of the Innocents by ‘Herod the king’ (assumed to be Herod the Great), who died in that year. Others believe that he was born about 6 AD, because that was the year of the Judean census that (allegedly) caused Joseph to travel to what was thought to be his ancestral home in Bethlehem. However, both these notions are based on myths and misunderstandings. The Jewish historian Josephus appears to know nothing of such a massacre and the taxation in Judaea did not involve the mass migration implied by Luke’s fanciful account.
Some astronomers believe that Jesus must have been born in 7 BC when there was a planetary conjunction which they (foolishly) think could account for the Star. This idea goes back at least Johannes Kepler in 1614. They do not realize that the story of the Star was invented from forecast in obscure Jewish books like the Pseudepigrapha and the Talmud.
There is no reason to doubt the calculation of the Scythian monk Dionysius Exiguus who, in what we now call 525 AD but was then the Roman year 754, decided to date years based on the (assumed) age of Jesus (others had done this occasionally before him). He based this on an assumed birth in 1BC. This dating system has been used in Christian countries since the Venerable Bede adopted it in the eighth century and it is now universal. To Christians, Jesus is now 2014 years old; in reality, he died in 33.
So let us all celebrate the Winter Solstice and the return of the sun and forget about Christ.
For more on all this, see my book The Rise and Fall of Jesus.