Christmas is the celebration of the birth of Christ. Although many of the traditions associated with Christmas and even the day on which is celebrated have pagan origins.
Most likely Christ was not born on December 25th. The weather conditions at that time of the year would have made it unlikely Mary & Joseph would have been able to spend the night in the stable. The stable was not like the barns we think of today but rather a cave or other crude structure. December 25th comes from pagan winter festivals and was an attempt by the church to Christianize pagan customs.
The arrival of the Magi did not occur on the night of Christ’s birth. The Magi did not arrive until approximately two years after the birth of Christ. That is why in Matthew’s account of the Magi’s visit, King Herod had all of the boys under the age of two killed.
Knowing the actual date of Christ’s birth is not as crucial as understanding the significance of his birth. Understanding significance of his birth and the prophecies fulfilled by his birth, life, death and resurrection and who he was are is foundational to Christian faith.