'Indiction' definitions:

Definition of 'indiction'

noun

A 15-year cycle used as a chronological unit in ancient Rome and adopted in some medieval kingdoms

From: GCIDE

Indiction \In*dic"tion\, n. [L. indictio: cf. F. indiction. See Indict, Indite.] [1913 Webster]
1. Declaration; proclamation; public notice or appointment. [Obs.] "Indiction of a war." --Bacon. [1913 Webster]
Secular princes did use to indict, or permit the indiction of, synods of bishops. --Jer. Taylor. [1913 Webster]
2. A cycle of fifteen years. [1913 Webster]
Note: This mode of reckoning time is said to have been introduced by Constantine the Great, in connection with the payment of tribute. It was adopted at various times by the Greek emperors of Constantinople, the popes, and the parliaments of France. Through the influence of the popes, it was extensively used in the ecclesiastical chronology of the Middle Ages. The number of indictions was reckoned at first from 312 a. d., but since the twelfth century it has been reckoned from the birth of Christ. The papal indiction is the only one ever used at the present day. To find the indiction and year of the indiction by the first method, subtract 312 from the given year a. d., and divide by 15; by the second method, add 3 to the given year a. d., and the divide by 15. In either case, the quotient is the number of the current indiction, and the remainder the year of the indiction. See Cycle of indiction, under Cycle. [1913 Webster]