quad·ri·cen·ten·a·ry 
(kwŏd′rĭ-sĕn-tĕnə-rē, -sĕntə-nĕr′ē)
(kwŏd′rĭ-sĕn-tĕnə-rē, -sĕntə-nĕr′ē)n. pl. quad·ri·cen·ten·a·ries
A 400th anniversary or celebration.
adj.
Of or relating to a span of 400 years or to a 400th anniversary.
[From alteration of Latin quadringentī, quadrigentī, four hundred (on the model of such words as TERCENTENARY); see kwetwer- in the Appendix of Indo-European roots.]