Oops, it doesn't look like 'polar bear plunge day' is a national day..

Other days

healing

Healing Day
youth

Youth Day
ruby

Ruby Day
frozen yogurt

Frozen Yogurt Day
bounce

Bounce Day
one

One Day
nae nae

Nae Nae Day
stud

Stud Day
my little pony

My Little Pony Day
lumpy rug

Lumpy Rug Day