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

Other days

artists

Artists Day
boyfriend

Boyfriend Day
eat what you want

Eat What You Want Day
kiss a ginger

Kiss A Ginger Day
brow

Brow Day
bow tie

Bow Tie Day
ormille

Ormille Day
first love

First Love Day
slime

Slime Day
youth

Youth Day