How did Santa start Christmas?

Santa didn't start Christmas but is a myth based on St. Nick, and several other legends in history.

Christmas is celebrated in December because the early Christian church was trying to convert pagans who celebrated the winter solstice, which is also in December.

It is now known that Jesus, if he was indeed an actual person, would have been born in early April. This is based on the descriptions of the stars and of the manger.