As adjectives the difference between quincentennial and quincentenary
is that quincentennial is relating to a 500th anniversary while quincentenary is pertaining to a quincentenary; quincentennial.
As a noun quincentenary is
a five-hundredth anniversary.
quincentenary
English
Noun
(quincentenaries)
A five-hundredth anniversary.
Adjective
(-)
Pertaining to a quincentenary; quincentennial.