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

Other days

kale

Kale Day
get funky

Get Funky Day
bounce

Bounce Day
camera

Camera Day
bonang

Bonang Day
polyamory

Polyamory Day
boy friend

Boy Friend Day
self appreciation

Self Appreciation Day
latina equal pay

Latina Equal Pay Day
gum

Gum Day