Atheists celebrate Christmas as a party to manage to gloom of winter.
The Jews have Hanukkah, that is their own version of a winter festival I think. I think it's a similar time to Christmas as well.
For me it is just an effort to cheer myself and my family up during the darker times. I drink alcohol twice a year, once at Christmas and once on my birthday, they are evenly spaced out. I have a nice glass of whiskey and try to unwind a bit. I know Jesus wasn't born on Christmas day because the Romans didn't do their sensus in the winter months.
One day I will be balanced-alan, a man that works hard and makes time for leisure.