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

Other days

nail polish

Nail Polish Day
pick me

Pick Me Day
youth

Youth Day
slime

Slime Day
my little pony

My Little Pony Day
bubble bath

Bubble Bath Day
stud

Stud Day
reading

Reading Day
bow tie

Bow Tie Day
unicorn

Unicorn Day