We don't know when exactly when Jesus was born(could be the summer) and that case even the year. The bible is not persice when it comes to this matter so the do the early christian leaders do was genius. They want to mark a specific date to rebemer Jesus birth and they want to convert people aslo so.  So they pick a roman pagan holiday that was at the end of each year and replace it with the christain holiday christmas.  Christanity is very flexable at incorparting new thing to convert people. How do you thing the Christmas tree got started?