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

Other days

stud

Stud Day
book

Book Day
ponytail

Ponytail Day
fiancee

Fiancee Day
donate your hair

Donate Your Hair Day
lash

Lash Day
ruby

Ruby Day
offer

Offer Day
self care

Self Care Day
self appreciation

Self Appreciation Day