The indiction ( Latin indictiō = announcement, announcement) is a 15-year cycle for counting the year, which was often used from late antiquity to the end of the Middle Ages . Other names are "Imperial number", "Roman interest", "Gedingzeichen" or "zeichen ". In the modern era , their use declined, but calendar they would continue to provide and the Imperial Court used the indiction until its dissolution in 1806 .
In the Roman Empire, the word indictiō denoted an imperial edict to determine the taxation of taxes in kind on estates. The tax, which has been levied annually since the early 4th century , was reset every 15 years (after every third census ). Under Constantine I , the 15-year cycle had been adopted in 312 . Emperor Justinian I wrote 537 in the Novella 47 the use of indiction for all datings law before.
The indiction was common throughout the West for calendar calculations and remained in use even in North Africa, which had become Muslim, and on the Iberian Peninsula, alongside the Hijra dating and the Sapphic era .
The years within an indiction cycle are numbered consecutively as first indiction , second indiction ... or the corresponding Roman interest number is determined for each year . This always grows from 1 to 15 and then starts again at 1. Indication 15 is followed by indiction 1. It was not customary to number the cycles of the indiction. In order to chronologically classify a late antique or medieval document dated only by indiction, one needs further clues.
There are different styles of indiction, which differ in the beginning of the epoch year.
- The indictio Graeca (Constantinopolitana) ( ancient Greek Ἰνδικτιών , Gen. -ῶνος) begins on September 1 and was mainly used in the Byzantine Empire, Sicily and the papal chancellery until 1087 and under Frederick II and Henry (VII) . (This is why the church year of the Orthodox Churches also begins on September 1st to this day.)
- The indictio Bedana (caesarea) according to Beda begins on September 24th. Their use went back in the late Middle Ages in favor of the indictio Romana .
- The indictio Romana (pontificia) begins its year on December 25th or January 1st (New Year's indiction ) and was most common in the late Middle Ages.
- The indictio Senensis begins on September 8th and was only in use in Siena .
One difficulty in determining the time of medieval dating lies in the possibility that the beginning of the year for counting the indiction and the beginning of the year for counting the year of incarnation can be different.
The cycle of indications is older than the Christian era , which Dionysius Exiguus first described in the early 6th century. In order to determine the year of the Christian calendar for a given index or the index for a given year of the Christian calendar, Dionysius Exiguus gave two conversion formulas as examples to the year 525 . As usual in Roman mathematics, he used natural numbers and division with a remainder . In today's mathematical notation, the conversion formulas are:
J = 15 * Z + 12 + I
I = (J + 2) mod 15 + 1
In each case, I is the indiction, the largest part of which falls in the given year, J is the year of the Christian count and Z is the number of completed cycles of indiction. In Dionysius Exiguus, the year 525 of the Christian count has the index 3. Dionysius Exiguus gave the number of index cycles that had passed from the birth of Christ to the year 525 as 34 and thus fixed a certain year as the year of the birth of Christ.
The indication of the indiction for dates before the 4th century or after the 18th century is unusual. The formulas of Dionysius can, however, be used indefinitely. According to our current calendar, the indiction results for a year number by adding 2 to the year number, then dividing by 15, and increasing the remainder of this division by 1. For the year 2017, for example, this results in (2017 + 2): 15 = 2019: 15 = 134 remainder 9. So the year 2017 is mostly in the indiction 9 + 1 = 10.
For the years from 300 AD to 1799, the indiction can be read from the following table:
|Determination of the indiction||300||400||500|
The year 1392 is highlighted in color in the table, for which the table, following the colored marking, gives the indiction 15.
The cycle of indications has no relation to astronomy. However, this makes it usable for a time calculation that is independent of astronomy. In 1583, Joseph Justus Scaliger suggested counting the days after the Julian date with the epoch January 1, 4713 BC. BC , whose cycle length of 7980 years also includes the cycle length of the indiction of 15 years as a factor.
- Friedrich Karl Ginzel : Handbook of mathematical and technical chronology. 3rd volume. Hinrichs, Leipzig 1914, pp. 148–155.
- Hermann Grotefend : Pocket book of the time calculation of the German Middle Ages and the modern times. 14th edition. Hahn, Hanover 2007, p. 8 f. and p. 140.
- Otto Seeck : Indictio . In: Paulys Realencyclopadie der classischen Antiquity Science (RE). Volume IX, 2, Stuttgart 1916, Col. 1327-1332.
- Calendar Tools : Form for calculating the indiction for a given medieval date.
- Indications for the years 313 to 1602
- Hermann Grotefend : Pocket book of the time calculation of the German Middle Ages and the modern times . 14th edition, Hahn, Hannover 2007, p. 8 f. and p. 140
- Adolf Berger : Encyclopedic Dictionary of Roman Law , Transactions of the American Philosophical Society, Volume 43, Part 2, 1953, p. 499. Reprint 1991 Online
- Adolf Grohmann et al .: Arabische Chronologie, Arabische Papyruskunde (= Handbook of Oriental Studies, 1st section: The Near and the Middle East; Erg.-Bd. 2, Halbd. 1,1,2), Leiden and Cologne 1966, P. 33. Google Books
- http://anemi.lib.uoc.gr/php/pdf_pager.php?rec=/metadata/c/3/f/metadata-39-0000567.tkl&do=153042.pdf&pageno=47&width=348&height=626&maxpage=386&lang= en
- Kerstin Springsfeld: Alkuins influence on computistics at the time of Charlemagne . Dissertation, Technical University Aachen 2000, Franz Steiner Verlag 2002, ISBN 3-515-08052-X , p. 172. Online