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

Other days

kale

Kale Day
hoodie

Hoodie Day
lumpy rug

Lumpy Rug Day
comfy

Comfy Day
one

One Day
youth

Youth Day
bonang

Bonang Day
offer

Offer Day
bounce

Bounce Day
lisp

Lisp Day