duodecennial

Etymology
From + English, equivalent to borrowing the unattested duodecennialis.

Adjective

 * 1) Consisting of twelve years, occurring in 12-year cycles.
 * 2) Occurring once a duodecade, occurring every 12 years.
 * 1) Occurring once a duodecade, occurring every 12 years.

Translations

 * Latin: duodecennialis