It isn't really an atheist holiday. It is mostly a joke people make when they are sick of all the Christmas specials, crazy lines at stores, and Christmas music every where.
“...It is mostly a joke people make when they are sick of all the Christmas specials...”
It’s more about mocking Kwanzaa, the made up holiday.
I personally look forward to the Sun reaching its southernmost declination.
Festivus is just as legit as Kwanzaa.