Take a seat, over there on the couch... X-D
Seriously, I don't think the exact date is that important, establishing it accurately would be well nigh impossible beyond the year (yes I know not the year 0 ;-) ) and as too conflicting religions, I think the name 'christmas' says it all even if the arbitrarily chosen date corresponds with a few native tribal celebrations in North America.
I would have to disagree, all though the origins of halloween (in the loosest sense) go back to celtic culture, the actual date used now is a spin off of all saints eve. A superstition that developed (slightly more than a few decades ago ;-) ) evolving from a fear of the night before all saints day. I think the Catholic Church could indirectly claim fatherhood of the modern halloween, ironically ;-)
God Bless,
Nathan
who normally carves a pumpkin or two or three...