Oops, it doesn't look like 'sub ur ex day' is a national day..

Other days

artists

Artists Day
cuddle up

Cuddle Up Day
cursing

Cursing Day
ormille

Ormille Day
frozen yogurt

Frozen Yogurt Day
boy friend

Boy Friend Day
hannah

Hannah Day
cat girl

Cat Girl Day
carpenters

Carpenters Day
singles

Singles Day