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

Other days

bow tie

Bow Tie Day
self appreciation

Self Appreciation Day
hoodie

Hoodie Day
stud

Stud Day
slime

Slime Day
fiancee

Fiancee Day
camera

Camera Day
gum

Gum Day
donate your hair

Donate Your Hair Day
ride the wind

Ride The Wind Day