Indiction

Ancient RomanHistorical unit (no longer in standard use)

A 15-year tax cycle introduced under the Roman Empire and used to date documents in the Byzantine and medieval worlds.

1 indiction = 473,354,280 seconds (exactly).

About the indiction

Indictions began as periodic reassessments of land or poll taxes in the Roman Empire, and the Latin indictio means an imposition or levy. Evidence exists for a 15-year cycle across the empire, a 14-year cycle in Roman Egypt, and a five-year cycle. Tax changes and arrears remissions tended to fall at the start of a cycle, with examples recorded under Nero in 58 AD and Hadrian in 118 AD.

Constantine is credited with turning the 15-year cycle into a dating system in 312 AD, and Egypt used it by 314 AD, though sources disagree on the first year, with one Coptic document implying 297 to 298. Justinian required indictions in dated documents in 537 AD. The year began on 23 September in the early Eastern Empire, later moving to 1 September, while Bede gives 24 September for the West and papal practice started on 25 December or 1 January. Because the length is a convention of 15 years, the figure used here is 15 Gregorian years, about 473.4 million seconds. The cycle also forms part of the 7,980-year Julian Period.

Sources: Wikipedia: Indiction

Indiction conversion chart

1 indiction expressed in every other time unit:

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