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

Other days

china

China Day
lisp

Lisp Day
kiss a brunette

Kiss A Brunette Day
buddy

Buddy Day
lumpy rug

Lumpy Rug Day
gum

Gum Day
kale

Kale Day
coffee

Coffee Day
singles

Singles Day
believe

Believe Day