vicennial

For comparison, the June 1963 value is comparable to a vicennial flood event, and is thus considered not that exceptional.

That's why I can't quite bring myself to use texting's vicennial as an occasion for wallowing in false nostalgia.

In 1981, he received the Vicennial Medal in recognition of his distinguished 20 years of service.

Vicennial Gold Medal for Distinguished Service, Georgetown University (1990)

While Fritz was working for the U.S. government he complied what is known as Research in the service of national purpose; proceedings of the Office of Naval Research Vicennial Convocation, in 1966.