Oops, it doesn't look like 'writing acknowledgement of invoice for writing day' is a national day..

Other days

bow tie

Bow Tie Day
girl friend

Girl Friend Day
carpenters

Carpenters Day
bounce

Bounce Day
brow

Brow Day
boy friend

Boy Friend Day
self care

Self Care Day
first love

First Love Day
ride the wind

Ride The Wind Day
reading

Reading Day