Festivus is NOT for the rest of us, but if you're looking for an alternative holiday on December 25th, there is Newtonmas, the documented birthday of Isaac Newton*. Or...→[More:]
Looking at the Wikipedia entry for December 25th, it's also the birthday of...
Clara Barton
Conrad Hilton
Robert Ripley, Believe It Or Not!
Humphrey Bogart
Cab Calloway
Quentin Crisp
Anwar Sadat
Rod Serling
Jimmy Buffett
Barbara Mandrell
Sissy Spacek
Karl Rove
CCH Pounder
Annie Lennox
...something for just about anybody. Merry Rovemas!

*which has apparently become enough of a "Geek Thing" to become a joke on The Big Bang Theory