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

Other days

lisp

Lisp Day
tulip

Tulip Day
hiv awareness

Hiv Awareness Day
artists

Artists Day
cuddle up

Cuddle Up Day
pumpkin

Pumpkin Day
ride the wind

Ride The Wind Day
gum

Gum Day
lumpy rug

Lumpy Rug Day
ormille

Ormille Day