Oops, it doesn't look like 'organizations to encourage coordination between day' is a national day..

Other days

one

One Day
kiss a brunette

Kiss A Brunette Day
frozen yogurt

Frozen Yogurt Day
self care

Self Care Day
hoodie

Hoodie Day
me

Me Day
lost sock memorial

Lost Sock Memorial Day
singles

Singles Day
blanket fort

Blanket Fort Day
cuddle up

Cuddle Up Day