quatercentenary(n = noun.time) quatercentennial - the 400th anniversary (or the celebration of it);
is a kind of anniversary, day of remembrance
quatercentenary, n. & adj.
--n. (pl. -ies)
1 a four-hundredth anniversary.
2 a festival marking this.
--adj. of this anniversary.
Etymology:
L quater four times + CENTENARY