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

Other days

lash

Lash Day
ponytail

Ponytail Day
kiss a ginger

Kiss A Ginger Day
pick me

Pick Me Day
youth

Youth Day
slime

Slime Day
blanket fort

Blanket Fort Day
ruby

Ruby Day
kiss a brunette

Kiss A Brunette Day
ormille

Ormille Day