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

Other days

first love

First Love Day
ride the wind

Ride The Wind Day
lumpy rug

Lumpy Rug Day
stud

Stud Day
youth

Youth Day
slime

Slime Day
bounce

Bounce Day
me

Me Day
boyfriend

Boyfriend Day
ask out your crush

Ask Out Your Crush Day