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

Other days

bow tie

Bow Tie Day
tulip

Tulip Day
cursing

Cursing Day
buddy

Buddy Day
my little pony

My Little Pony Day
bubble bath

Bubble Bath Day
stud

Stud Day
lisp

Lisp Day
boy friend

Boy Friend Day
first love

First Love Day