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

Other days

hoodie

Hoodie Day
stress awareness

Stress Awareness Day
pick me

Pick Me Day
lumpy rug

Lumpy Rug Day
gum

Gum Day
me

Me Day
eat what you want

Eat What You Want Day
one

One Day
reading

Reading Day
unicorn

Unicorn Day