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

Other days

gum

Gum Day
brow

Brow Day
carpenters

Carpenters Day
eat what you want

Eat What You Want Day
law

Law Day
lash

Lash Day
boba

Boba Day
cuddle up

Cuddle Up Day
latina equal pay

Latina Equal Pay Day
mean girls

Mean Girls Day