duodecennial's Usage Examples:

Māmānkam or Māmāngam was a duodecennial medieval fair held on the bank, and on the dry river-bed, of Pērār (River Nil̥a, River Ponnani, or Bhārathappuzha).

staff, but the site drew thousands each year and up to 50,000 on its duodecennial festivals (every twelve years).

constellations of the zodiac and the years named for the animals of the duodecennial cycle; it remained in use until 1925.

one of the twelve Earthly Branches representing the years of Jupiter's duodecennial orbital cycle.

duplex, duumvirate, duumviri, nonduality duodecim duodec- twelve dozen, duodecennial, duodecillion duodecimus duodec- twelfth duodecimal duodeni duoden- twelve.