Editing Indiction (section)

==Calculation==
A useful chart providing all the equivalents can be found in Chaîne's book on chronology,<ref>Chaîne, Marius. 1925. ''La chronologie des temps chrétiens de l’Égypte et de l’Éthiopie''. Paris: Librairie Orientaliste Paul Geuthner.</ref> and can easily be consulted online at the Internet Archive, from [[iarchive:lachronologiedes0000chan/page/134/mode/2up|page 134]] to [[iarchive:lachronologiedes0000chan/page/172/mode/2up|page 172]]. 

The Roman indiction for a modern [[Anno Domini]] year ''Y'' (January 1 to December 31) may be calculated as follows:<ref>Blackburn & Holford-Strevens p. 771</ref>
:(''Y'' + 3) [[Modular arithmetic|mod]] 15

For example, the indiction for the year 2017 is 10:<ref>"Calendars" p. B4</ref>
:(2017 + 3) mod 15 = 10

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:

:(2022+3) mod 15 = 0

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 the '''mod''' operation:
:(''Y'' + 2) mod 15 + 1

That yields the expected answer, for 2022 again:
:(2022+2) mod 15 + 1 = 15