It is said that the Virgin Mary, the mother of Jesus, became pregnant with the Holy Spirit.
When Maria was about to give birth, the Rome government ordered that all the people had to declare their residence in Bethlehem.
Mary and her fiance Joseph had to go to Bethlehem. When they arrived in Bethlehem, they were unable to find hotel accommodation, only a stable was available for temporary stay. Just then, Jesus was about to be born. So Mary gave birth to Jesus in the manger.
In order to commemorate the birth of Jesus, we designated December 25 as Christmas. In fact, there is no clear record of the birth date of Jesus in the Bible. It was not officially designated as Christmas until December 25 in the third century.
Some Eastern Orthodox denominates January 6 and 7 as Christmas.