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

Other days

slime

Slime Day
frozen yogurt

Frozen Yogurt Day
kiss a brunette

Kiss A Brunette Day
law

Law Day
blanket fort

Blanket Fort Day
coffee

Coffee Day
cuddle up

Cuddle Up Day
offer

Offer Day
boyfriend

Boyfriend Day
girl friend

Girl Friend Day