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

Other days

slime

Slime Day
fiancee

Fiancee Day
lash

Lash Day
girl friend

Girl Friend Day
cursing

Cursing Day
boy friend

Boy Friend Day
ride the wind

Ride The Wind Day
bubble bath

Bubble Bath Day
mean girls

Mean Girls Day
bounce

Bounce Day