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

Other days

slime

Slime Day
self care

Self Care Day
ponytail

Ponytail Day
reading

Reading Day
pampering

Pampering Day
brow

Brow Day
carpenters

Carpenters Day
pumpkin

Pumpkin Day
artists

Artists Day
blanket fort

Blanket Fort Day