quadracentennial

1. alternativenot comparableAlternative form of quadricentennial

   [...] the quadracentennial celebration coincided with the 150-year anniversary of the signing of the Treaty of Guadeloupe Hidalgo.

   2002, The Political Life of Forests in Northern New Mexico, page 68

   1 more example

   [...] the quadracentennial celebration to be held in 1965, and proposed that this Club begin plans for a commemorative medal to be issued then.

   1961, The Numismatist, page 704

plural quadracentennials

1. alternativeAlternative form of quadricentennial

   [...] the quadracentennial of his death.

   1962, No Other Foundation, page 43

   2 more examples

   [...] the quadracentennial of the posting of the Ninety-five Theses at Wittenberg in 1517.

   1979, Trials and Triumphs, page 22

   [...] the quadracentennial of Columbus in 1892.

   1996, Lithuanian Religious Life in America, page 41