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

Other days

gum

Gum Day
girl friend

Girl Friend Day
buddy

Buddy Day
hannah

Hannah Day
cat girl

Cat Girl Day
nae nae

Nae Nae Day
eat what you want

Eat What You Want Day
china

China Day
bounce

Bounce Day
ponytail

Ponytail Day