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Anindiction (Latin:indictio, impost) was a periodic reassessment of taxation in theRoman Empire which took place every fifteen years. InLate Antiquity, this 15-year cycle began to be used to date documents and it continued to be used for this purpose inMedieval Europe,[1] and can also refer to an individual year in the cycle; for example, "the fourth indiction" came to mean the fourth year of the current indiction. Since the cycles themselves were not numbered, other information is needed to identify the specific year.
Indictions originally referred to the periodic reassessment for an agricultural or land tax in theRoman Empire. There were three different cycles: a 15-year cycle used throughout the empire; a 14-year cycle used inRoman Egypt; and a five year cycle called thelustrum, derived from theRoman Republican census. Changes to the tax system usually took place at the beginning of one of these cycles and at the end of the indictionEmperors often chose to forgive anyarrears. The 15-year cycle can be traced in literary and epigraphic references to taxation reforms and the cancellation of arrears.[2]
TheChronicon Paschale (c. 630 AD) claims that the 15-year cycle was instituted byJulius Caesar in 49 BC, which was also the first year of the Antiochene era, but there is no other evidence for this and, if the cycle were the same one known from later periods, the start date ought to be 48 BC.[3] The earliest known event associated with the 15-year cycle is the establishment of a special board of threepraetors to pursue arrears for the cycle ending in 42 AD, underClaudius.[4][5] The beginning of the cycle in 58 AD coincides with a set of tax reforms and remissions instituted byNero.[6][5]Vespasian carried out a census of Italy at the start of the next indiction in 73 AD[7][5] The indiction starting in 103 AD may coincide with the tax remission byTrajan depicted on thePlutei of Trajan.[5] At the start of the next indiction in 118 AD,Hadrian wrote off 900,000,000sesterces of tax arrears, which he refers to in an inscription as the largest remission ever granted.[8][5] He again remitted arrears at the start of the next indiction in AD 133,[9][5] as didAntoninus Pius at the start of the next indiction in 148 AD.[10][5]Marcus Aurelius andCommodus carried out another remission at the start of the indiction beginning in 178 AD.[11][5]
The 14-year cycle used in Egypt derived from the fact that liability for the Egyptianpoll tax began at the age of fourteen, necessitating a new survey of the population every fourteen years. Tax reforms and remissions recorded inpapyrus sources indicate that it was also in existence in the first century AD.[12] The first evidence is an edict byMarcus Mettius Rufus, thePrefect of Egypt in AD 89, requiring property and loans to be registered.[13][12] The next cycle in 103 AD coincides with reforms to record-keeping.[14][12] The beginning of the cycle in 117 AD coincided with the 15-year cycle and was the occasion of Hadrian's large tax remission.[12] This 14-year cycle is last attested in 257 AD.[15] From 287 AD, at the latest, Roman Egypt used a system of 5-year cycles, then a non-cyclic series which reached number 26 by 318 AD.[16]
The 15-year cycle was introduced as a dating system on documents throughout the Roman empire byConstantine in 312 AD and it was in used in Egypt by 314 AD.[17] TheChronicon Paschale (c. 630 AD) assigned its first year to 312–313 AD, whereas aCoptic document of 933 AD assigned its first year to 297–298 AD, one cycle earlier. Both of these were years of theAlexandrian calendar whose first day wasThoth 1 on August 29 in years preceding commonJulian years and August 30 in years preceding leap years, hence each straddled two Julian years. The reason for beginning the year at that time was that the harvest would be in, and so it was an appropriate moment to calculate the taxes that should be paid.
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 theMediterranean. In theEastern Roman Empire outside of Egypt, the first day of its year was September 23, the birthday ofAugustus. During the last half of the fifth century, probably 462 AD, this shifted to September 1, where it remained throughout the rest of theByzantine Empire. In 537 AD,Justinian decreed that all dates must include the indiction viaNovella 47,[18] which eventually caused the Byzantine year to begin onSeptember 1.[clarification needed] But in the western Mediterranean, its first day wasSeptember 24 according toBede, or the followingDecember 25 orJanuary 1, called the papal indiction. Anindictio Senensis beginningSeptember 8 is sometimes mentioned.
The 7,980-yearJulian Period was formed by multiplying the 15-year indiction cycle, the 28-yearsolar cycle and the 19-yearMetonic cycle.
When the term "indiction" began to be used, it referred only to the full cycle, and individual years were referred to as being Year 1 of the indiction, Year 2 of the indiction, etc. It gradually became common to apply the term to the years themselves, which thus became the first indiction, the second indiction, and so on.
A useful chart providing all the equivalents can be found in Chaîne's book on chronology,[19] and can easily be consulted online at the Internet Archive, frompage 134 topage 172.
The Roman indiction for a modernAnno Domini yearY (January 1 to December 31) may be calculated as follows:[20]
For example, the indiction for the year 2017 is 10:[21]
However, this formula will produce an error for the last year of an indiction, where the modulo value is 0 instead of the expected 15, as can be seen when applying it to the year 2022:
One can simply read 0 as 15, but in order to have the correct result directly, the addition of a value of 1 from the offset may be delayed until after themod operation:
That yields the expected answer, for 2022 again:
