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

Other days

slime

Slime Day
bow tie

Bow Tie Day
reading

Reading Day
kiss a ginger

Kiss A Ginger Day
self appreciation

Self Appreciation Day
gum

Gum Day
girl friend

Girl Friend Day
camera

Camera Day
unicorn

Unicorn Day
ponytail

Ponytail Day