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

Other days

ask out your crush

Ask Out Your Crush Day
self care

Self Care Day
law

Law Day
lisp

Lisp Day
hoodie

Hoodie Day
offer

Offer Day
youth

Youth Day
my little pony

My Little Pony Day
buddy

Buddy Day
eat what you want

Eat What You Want Day