quatercentenary
Concise Oxford English Dictionary © 2008 Oxford University Press:
quatercentenary /ˌkwatəsɛnˈtiːn(ə)ri, -ˈtɛn-, ˌkweɪtə-/
▶noun (pl. quatercentenaries) a four-hundredth anniversary.
'quatercentenary' also found in these Oxford entries:

