Indiction

The indiction is a 15-year cycle used to date medieval documents throughout Europe, both East and West. Each year was numbered: first indiction, second indiction, etc. However, the cycles were not numbered, thus other information is needed to identify the specific year.

Indictions originally referred to an agricultural or land tax in late third-century Roman Egypt. These were originally in 5-year cycles beginning in 287, then in a non-cyclic series which reached number 26 by 318. But by 314 the 15-year cycle had appeared. The Chronicon Paschale (c. 630) assigned its first year to 312-313, whereas a Coptic document of 933 assigned its first year to 297-298, one cycle earlier. Both of these were years of the Alexandrian calendar whose first day was Thoth 1 on August 29 in years preceding common Julian years and August 30 in years preceding leap years, hence each straddled two Julian years.

The indiction was first used to date documents unrelated to tax collection in the mid-fourth century. By the late fourth century it was being used to date documents throughout the Mediterranean. In the Eastern Roman Empire outside of Egypt, the first day of its year was September 23, the birthday of Augustus. During the last half of the fifth century, probably 462, this shifted to September 1, where it remained throughout the rest of the Byzantine Empire. In 537 Justinian decreed that all dates must include the indiction via Novella 47, which eventually caused the Byzantine year to begin on September 1. But in the western Mediterranean, its first day was September 24 according to Bede, or the following December 25 or January 1, called the papal indiction. An indictio Senensis beginning September 8 is sometimes mentioned.

The 7980-year Julian Period was formed by multiplying the 15-year indiction cycle, the 28-year solar cycle and the 19-year Metonic cycle.

Possible Indiction values are 1 to 15. The indiction for an historical Anno Domini year between January 1 and December 31 following September 1, 23, or 24 can be calculated by taking the remainder of the year plus 2 divided by 15 and adding 1 to it. For example: the Indiction for the year 1999 is 7 [(1999 + 2) mod 15 + 1 = 7]. So 2008 is the first year of the Indiction. (2008+2) mod 15 +1 = 16 or 1.

Alternatively, the indiction for the year of the Byzantine era beginning September 1 is found by dividing by 15. In both cases, the remainder is the indiction, but if the remainder is zero, then the indiction is 15.

References

• Yiannis E. Meimaris, Chronological systems in Roman-Byzantine Palestine and Arabia (Athens, 1992), 32-34
• Chronicon paschale 284–628 AD, trans. Michael Whitby, Mary Whitby (Liverpool, 1989), 10.
• Leo Depuydt, "AD 297 as the beginning of the first indiction cycle", The bulletin of the American Society of Papyrologists, 24 (1987): 137-9.
• Roger S. Bagnall, K. A. Worp, The chronological systems of Byzantine Egypt (Zutphen, 1978).
• Bonnie Blackburn, Leofranc Holford-Strevens, The Oxford companion to the year (Oxford, 1999), 769-71.
• V[enance] Grumel, "Indiction", New Catholic encyclopedia.
• S. P. Scott [Justinian I], "Forty-seventh new constitution" [Novella 47], The civil law [Corpvs jvris civilis] (1932; reprinted New York, 1973), 16 (in 7): 213-15.
• Dates and dating