If you look up the origins of Christmas, you'll see that it actually celebrates Jesus Christ's birth. (God's son). Jesus came down to this earth to die and to pay for our sins on the cross. Then he rose from the dead! (Easter). God loves you, and...
Excuse my boldness, but why did you become an atheist? If you humbly ask God to show himself to you, he will! it's as simple as that- just a little faith!