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

Other days

gum

Gum Day
lash

Lash Day
embarrass your best friend

Embarrass Your Best Friend Day
stud

Stud Day
unicorn

Unicorn Day
boba

Boba Day
singles

Singles Day
pick me

Pick Me Day
boy friend

Boy Friend Day
coffee

Coffee Day