Editing Indiction (section)

===Late Antiquity and Middle Ages===
The 15-year cycle was introduced as a dating system on documents throughout the Roman empire by [[Constantine the Great|Constantine]] in 312 AD and it was in used in Egypt by 314 AD.<ref>Duncan-Jones 1994 p.&nbsp;63.</ref> The ''[[Chronicon Paschale]]'' (c. 630 AD) assigned its first year to 312–313 AD, whereas a [[Coptic Orthodox Church of Alexandria|Coptic]] document of 933 AD assigned its first year to 297–298 AD, one cycle earlier. Both of these were years of the [[Alexandrian calendar]] whose first day was [[Thout|Thoth]]&nbsp;1 on August 29 in years preceding common [[Julian calendar|Julian 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 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 AD, this shifted to September 1, where it remained throughout the rest of the [[Byzantine Empire]]. In 537 AD, [[Justinian]] decreed that all dates must include the indiction via {{nowrap|Novella 47}},<ref>Constitutiones 4.21: De fide instrumentorum et amissione eorum et antapochis faciendis et de his quae sine scriptura fieri possunt; Novellae 47, 73.</ref> which eventually caused the Byzantine year to begin on {{nowrap|September 1}}.{{Clarify|date=April 2024|reason=How the primary source is relevant is not made clear - additional sources may be helpful?}} But in the western Mediterranean, its first day was {{nowrap|September 24}} according to [[Bede]], or the following {{nowrap|December 25}} or {{nowrap|January 1}}, called the papal indiction. An ''indictio Senensis'' beginning {{nowrap|September 8}} is sometimes mentioned.

The 7,980-year [[Julian Period#History|Julian Period]] was formed by multiplying the 15-year indiction cycle, the 28-year [[solar cycle (calendar)|solar cycle]] and the 19-year [[Metonic cycle]].