Oops, it doesn't look like 'dumb ass day' is a national day..

Other days

slime

Slime Day
polyamory

Polyamory Day
tulip

Tulip Day
kale

Kale Day
cuddle up

Cuddle Up Day
mean girls

Mean Girls Day
ride the wind

Ride The Wind Day
one

One Day
kiss a brunette

Kiss A Brunette Day
camera

Camera Day