quin·cen·ten·a·ry 
(kwĭn′sĕn-tĕnə-rē, kwĭn-sĕntə-nĕr′ē)
(kwĭn′sĕn-tĕnə-rē, kwĭn-sĕntə-nĕr′ē)n. pl. quin·cen·ten·a·ries
A 500th anniversary or celebration.
adj.
Of or relating to a span of 500 years or to a 500th anniversary.
[From Latin quīngentī, quīncentī, five hundred (on the model of such words as TERCENTENARY); see penkwe in the Appendix of Indo-European roots.]