Oops, it doesn't look like 'be an arsehole day' is a national day..

Other days

buddy

Buddy Day

brow

Brow Day

eat what you want

Eat What You Want Day

slime

Slime Day

Emoji Day

tell a fairytale

Tell A Fairytale Day

cuddle up

Cuddle Up Day

boba

Boba Day

boyfriend

Boyfriend Day

tell ur crush you like them

Tell Ur Crush You Like Them Day