Christmas is a Christian holiday. It's been made available for everyone through commercialization in the media and in the culture by such things as Frosty The Snowman and Rudolph The Red-nosed Reindeer and Santa Claus.
Let me rephrase: The salvation of Christ and the redemption of sin that He offers, is available to all. Christmas is the day on which Christians celebrate the birth of the Savior of mankind, and this is good news for everyone on the planet.