"Decorating trees" came from Germany by the way.
"Certain celebrations". American holidays didn't last thousands of years, heck neither has america lol. If that's what you mean by certain celebrations.
Who says you have to believe in it to join it? I don't believe partaking in the ritual of eating pizza will bring me true happiness, but I eat it anyways.
He wasn't born in December, I forget exactly what month and such, not sure...
You just acknowledge that he was born, just so happens you do that in Decemember. I don't need a holiday or any day to tell me to realize the truth though. Valentine's Day is such a scan. Cost to much gosh darn money lol, oh it adds up over the years.