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

Other days

boba

Boba Day
cuddle up

Cuddle Up Day
donate your hair

Donate Your Hair Day
prosecco

Prosecco Day
one

One Day
kale

Kale Day
camera

Camera Day
law

Law Day
offer

Offer Day
fiancee

Fiancee Day