It's the day of Jesus', our lord and savior, birth! Of course, it's actually not--Jesus was born in the summer and Christmas is just a Christianization of the Roman holiday, Saturnalia. So really, it's the perfect day to disrespect the lord that never is, was, or will be.
I think our friend Ivan Brunetti can help illustrate how the Christian God is a disgusting lie! This strip is from Schizo #1.