The Gospel of Matthew is the oldest of the gospels and was written some time after 70AD. It is the only gospel which mentions either the Star of Bethlehem or the Magi. From Mark 6:1-4, we see that the author of the Gospel of Mark did not appear to be aware of the Bethlehem nativity story. The gospel of Matthew depicts a royal Jesus, with celestial events heralding his birth. The gospel of Luke shows Jesus of humble origins, linked to shepherds.

The Gospel of John states that Jesus was from Galilee, and not Bethlehem. The Gospels often described Jesus as "of Nazareth," but never as "of Bethlehem". The Matthew account conflicts with the Gospel of Luke, in which the family of Jesus already lived in Nazareth, traveled to Bethlehem for the census, and returned home almost immediately.

A very close conjunction between Jupiter and Venus occurred on June 17, 3 BC. The apparent fusion of two planets would have been a rare and awe-inspiring event. That event occurred after the generally accepted date of 4 BC for the death of Herod.

According to the biblical account, the three wise men, motivated by a “star in the east,” first traveled to Jerusalem, and asked King Herod (Matthew 2:1—2) where the newborn King of the Jews could be found. Clearly, they knew that the birth had occurred. [Naturally, we want to know how they knew, but there is no explanation.] Also, since Herod was alive, and the Magi inquired about the birth of Jesus, it follows that Matthew put the birth of Jesus before the death of Herod in 4 BC.

We also need to think about King Herod, who asked the wise men when the star had appeared. Apparently, he and his court were unaware of any such star in the sky (Matthew 2:7—10). These events present us with an astronomy puzzle: How could King Herod’s own advisors have been unaware of a star so bright and obvious that it could have led the wise men to Jerusalem?

Next, to reach Bethlehem, the wise men had to travel directly south from Jerusalem; somehow that “star in the east” “went before them, ‘til it came and stood over where the young child was.” There is no known phenomenon which could explain such behavior except in a figurative sense. Furthermore, since there was no light pollution at that time in history, there was no need to travel, as the conjunction would have been visible from anywhere.

The account in Matthew conflicts with the gospel of Luke. In (Luke 2:1—7), it states that Jesus was born when Quirinius was the governor of Syria to which post he was appointed in 6 AD. So, the gap between the accounts in Matthew and Luke is about 10 years. Some people have claimed that the Julian calendar was too inaccurate to fix dates correctly. While the Julian calendar (ordered by Julius Caesar in 45 BC) was not accurate in modern terms, its error was in the order of one day every 128 years, which is insufficient to support the claims that their calendar was too inaccurate to fix the date of Herod’s death.

Around 200 AD, Clement of Alexandria wrote: “… Others say that He was born on 25 April”. That claim is consistent with the Bible (Luke 2:7-8) which states that “Shepherds were in the fields …” which they would not have done during December. The precise origin of assigning December 25 as the birth date of Jesus is unclear. The New Testament provides no clues in this regard. December 25 was first identified as the date of the birth of Jesus by Sextus Julius Africanus in 221 AD, and it became the accepted date. Although most Christians celebrate December 25 as the birthday of Jesus Christ, few in the first two Christian centuries claimed any knowledge of the exact day or year in which he was born.

One widespread explanation of the origin of this date is that December 25 was the christianizing of the dies solis invicti nati, a popular holiday in the Roman Empire that celebrated the winter solstice. In fact, the early Catholic Church converted ALL of the feast days of the Roman religion into “holy days”. The first official mention of December 25 as a holiday honoring Jesus' birthday appears in an early Roman calendar from 336 A.D.

A detailed and scholarly treatment of this subject can be read at http://www.astronomynotes.com/history/bethlehem-star.html