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

Other days

hoodie

Hoodie Day
cuddle up

Cuddle Up Day
fiancee

Fiancee Day
ruby

Ruby Day
one

One Day
donate your hair

Donate Your Hair Day
blanket fort

Blanket Fort Day
boyfriend

Boyfriend Day
kiss a brunette

Kiss A Brunette Day
carpenters

Carpenters Day