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

Other days

fiancee

Fiancee Day
pumpkin

Pumpkin Day
buddy

Buddy Day
healing

Healing Day
slime

Slime Day
tell a fairytale

Tell A Fairytale Day
blanket fort

Blanket Fort Day
first love

First Love Day
promposal

Promposal Day
bounce

Bounce Day