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

Other days

boba

Boba Day
slime

Slime Day
ormille

Ormille Day
mean girls

Mean Girls Day
lisp

Lisp Day
bow tie

Bow Tie Day
nail polish

Nail Polish Day
kiss a brunette

Kiss A Brunette Day
girl friend

Girl Friend Day
gum

Gum Day