Oops, it doesn't look like 'slap an idiot day' is a national day..

Other days

gum

Gum Day
pick me

Pick Me Day
brow

Brow Day
tulip

Tulip Day
nae nae

Nae Nae Day
pumpkin

Pumpkin Day
lost sock memorial

Lost Sock Memorial Day
bubble bath

Bubble Bath Day
slime

Slime Day
kiss a brunette

Kiss A Brunette Day