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

Other days

tulip

Tulip Day
bubble bath

Bubble Bath Day
unicorn

Unicorn Day
book

Book Day
frozen yogurt

Frozen Yogurt Day
kale

Kale Day
eat what you want

Eat What You Want Day
brow

Brow Day
lost sock memorial

Lost Sock Memorial Day
aloxolt

Aloxolt Day