Jesus was born 6 months after John the Baptist, who was born in the spring , March/ April , this would place the birth of Messiah September/October sometime during a holy day of the Jews. It was yet warm outside in September/October and the shepherds could still tend to their flocks outside but in December the sheep were inside due to cold weather. During the Jewish holy days thousands of Jews travelled to the area around and in Jerusalem to keep the feast as commanded by the Law of Moses. This is why there was no room at the inn. According to some scholars the taxing ordered by Caesar Augustus took place during the fall harvest both Joseph and Mary traveled to Bethlehem to register, Luke 2:3 .