How did Japanese era names work before the Issei ichigen system? I know starting with Meiji they had Eras defined by the ruler (Meiji, Taisho, Showa, Heisei, Reiwa), but before that it was more complicated with there being multiple eras during one rule. For instance, Koukaku had the Tenmei, Kansei, Kyouwa, and Bunka eras.

How exactly did they decide where an era started and ended without using the incumbent Emperor to decide it?

  • 2
    There actually appears to be a Wikipedia page for that. However, I'm having trouble wrapping my head around it even reading the WP page, so IMHO this is still a good question.
    – T.E.D.
    Jul 10, 2023 at 18:10
  • Quite right - I remember my impression that this is a surprisingly complex topic. IIRC the Taika reforms kept the same nominal government, but dates are calculated from the regulatory promulgation. There is a distinction that doesn't exist in any other history that I've studied.
    – MCW
    Jul 10, 2023 at 18:42
  • Having said that, the question should reference the relevant wiki page. It sounds like there wasn't a formal system...
    – MCW
    Jul 10, 2023 at 18:51
  • @MCW - I don't know... I got the impression that there was actually a formal system, but the problem is that there were several such systems depending on the date (and even some lost years where there indeed was no system). As they say: A man with a watch knows what time it is. A man with two watches is never sure.
    – T.E.D.
    Jul 11, 2023 at 14:23

1 Answer 1


I interpret the following quote to mean that there were multiple conflicting signals that would trigger a change to an era name, and that it may not be possible to clearly identify a system.

Prior to the Meiji period, era names were decided by court officials and were subjected to frequent change. A new era name was usually proclaimed within a year or two after the ascension of a new emperor. A new era name was also often designated on the first, fifth and 58th years of the sexagenary cycle, because they were inauspicious years in Onmyōdō. These three years are respectively known as kakurei, kakuun, and kakumei, and collectively known as sankaku. Era names were also changed due to other felicitous events or natural disasters. Wikipedia: Japanese Era Name

Aside: the metaphor that springs to mind is "Xnomics" when an elected official needs to shore up support or market for some initiative, they assign a catchy name and build stories around it. Activity that if it were carried out in the internet would be called "memage". I suspect that pre-Meiji era names were "memage".

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