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

Other days

stud

Stud Day
nae nae

Nae Nae Day
kiss a brunette

Kiss A Brunette Day
hoodie

Hoodie Day
slime

Slime Day
eat what you want

Eat What You Want Day
cuddle up

Cuddle Up Day
bow tie

Bow Tie Day
self care

Self Care Day
boba

Boba Day