Oops, it doesn't look like 'wear a show shirt as a real shirt day' is a national day..

Other days

bubble bath

Bubble Bath Day
boy friend

Boy Friend Day
martini

Martini Day
fiancee

Fiancee Day
me

Me Day
special education

Special Education Day
ormille

Ormille Day
blanket fort

Blanket Fort Day
bow tie

Bow Tie Day
cuddle up

Cuddle Up Day