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

Other days

unicorn

Unicorn Day
azonto is acceptable

Azonto Is Acceptable Day
promposal

Promposal Day
ormille

Ormille Day
hot chocolate

Hot Chocolate Day
bonang

Bonang Day
bow tie

Bow Tie Day
kale

Kale Day
ruby

Ruby Day
tulip

Tulip Day