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

Other days

frozen yogurt

Frozen Yogurt Day
offer

Offer Day
kiss a brunette

Kiss A Brunette Day
mean girls

Mean Girls Day
stud

Stud Day
nail polish

Nail Polish Day
kiss a ginger

Kiss A Ginger Day
gallery

Gallery Day
bonang

Bonang Day
tulip

Tulip Day