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

Other days

bow tie

Bow Tie Day
special education

Special Education Day
pampering

Pampering Day
self care

Self Care Day
believe

Believe Day
reading

Reading Day
ponytail

Ponytail Day
nail polish

Nail Polish Day
ormille

Ormille Day
singles

Singles Day