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

Other days

coffee

Coffee Day
lost sock memorial

Lost Sock Memorial Day
pick me

Pick Me Day
kale

Kale Day
one

One Day
promposal

Promposal Day
slime

Slime Day
lumpy rug

Lumpy Rug Day
tell a fairytale

Tell A Fairytale Day
stud

Stud Day