Oops, it doesn't look like 'Park And Zeus Cave day' is a national day..

Other days

boyfriend

Boyfriend Day
tulip

Tulip Day
ruby

Ruby Day
lumpy rug

Lumpy Rug Day
bow tie

Bow Tie Day
lost sock memorial

Lost Sock Memorial Day
buddy

Buddy Day
lisp

Lisp Day
reading

Reading Day
hoodie

Hoodie Day