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

Other days

china

China Day
coffee

Coffee Day
martini

Martini Day
frozen yogurt

Frozen Yogurt Day
cat girl

Cat Girl Day
nae nae

Nae Nae Day
chocolate milkshake

Chocolate Milkshake Day
self care

Self Care Day
mean girls

Mean Girls Day
lash

Lash Day