Holidarian
A person who celebrates religious holidays (such as Christmas, Hanukkah, Easter, etc) despite a complete lack of religious beliefs.
Joe: "Hey I heard you're having people over for Hanukkah. I didn't know you were Jewish!"
Phil: "Oh we're not Jewish, we're doing it because we're holidarians."
Phil: "Oh we're not Jewish, we're doing it because we're holidarians."