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

Other days

boy friend

Boy Friend Day
donate your hair

Donate Your Hair Day
kale

Kale Day
pumpkin

Pumpkin Day
bow tie

Bow Tie Day
stud

Stud Day
unicorn

Unicorn Day
first love

First Love Day
boba

Boba Day
fiancee

Fiancee Day