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

Other days

boyfriend

Boyfriend Day
self appreciation

Self Appreciation Day
artists

Artists Day
brow

Brow Day
promposal

Promposal Day
bow tie

Bow Tie Day
kiss a ginger

Kiss A Ginger Day
lumpy rug

Lumpy Rug Day
ride the wind

Ride The Wind Day
kiss a brunette

Kiss A Brunette Day