The week of Dec 21-25 was assigned by the older Catholic church...a date used by Romans on the solstice, when they worshipped the sun. The original Biblical calendar (Hebrew) was based on a 10 month year...not 12 months. The Romans added 2 months to make the current 12 month calendar....which puts Jesus's birth around the beginning of October. Read the book of Luke; sheep and shepards would not be outside in the dead of winter. And we still use the Biblical calendar in a sense: the last four months? Sept, Oct, Nov, Dec....or in latin is 7, 8, 9, 10.
Mind blown.