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

Other days

martini

Martini Day
nae nae

Nae Nae Day
unicorn

Unicorn Day
artists

Artists Day
bounce

Bounce Day
ask out your crush

Ask Out Your Crush Day
cuddle up

Cuddle Up Day
fiancee

Fiancee Day
gum

Gum Day
reading

Reading Day