Douglas Harper's Etymology Dictionary
quadricentennial
also quadri-centennial, 1859, from quadri- + centennial.
Wiktionary
quadricentennial
a. Relating to a 400th anniversary.
Usage examples of "quadricentennial".
Its overall mood was especially festive that spring, because its splendid Quadricentennial Exposition had opened only three weeks earlier, and eager visitors were flocking to this gleaming city on the River Fluss from all over Europe and beyond.