Japanese imperial eras, 1868–present
Japan numbers its years within an imperial era (元号, gengō) as well as by the Gregorian year. An era begins on the day of accession, not on 1 January, which is why a single Gregorian year can carry two era names and why two consecutive days can be labelled with years that look decades apart.
| Era | Kanji | First day | Last day | Final year of the era |
|---|---|---|---|---|
| Meiji era | 明治 | (Friday) | 明治45年 (Meiji 45) | |
| Taisho era | 大正 | (Tuesday) | 大正15年 (Taisho 15) | |
| Showa era | 昭和 | (Saturday) | 昭和64年 (Showa 64) | |
| Heisei era | 平成 | (Sunday) | 平成31年 (Heisei 31) | |
| Reiwa era | 令和 | (Wednesday) | Current era | — |
Why the first year is 元年 and not 1年
The year an era begins is its first year, however much of the Gregorian year is left. So the same Gregorian year is counted as the final year of the outgoing era up to the accession and as year one of the new era from the accession onwards. That first year is written 元年 (gannen), literally "origin year", rather than 1年.
A year in an era is therefore not a span of 365 days, and an era year cannot be converted to a Gregorian year without knowing the month and day. The table below is the same rule seen from the other side: four pairs of consecutive dates, each pair a day apart.
| Gregorian date | Era year |
|---|---|
| 明治45年 (Meiji 45) | |
| 大正元年 (Taisho 1) | |
| 大正15年 (Taisho 15) | |
| 昭和元年 (Showa 1) | |
| 昭和64年 (Showa 64) | |
| 平成元年 (Heisei 1) | |
| 平成31年 (Heisei 31) | |
| 令和元年 (Reiwa 1) |
Two of those pairs are worth reading twice. 7 January 1989 is Showa 64 and 8 January 1989 is Heisei 1 — Showa 64 lasted seven days in total. And 30 April 2019 is Heisei 31 while 1 May 2019 is Reiwa 1, the first accession in modern Japanese history to follow an abdication rather than a death, which is why that one date was known years in advance.
Where these dates come from and where they stop
The era boundaries are the dates of accession, held in this site's source as a typed table and used by both this page and the calculator, so the two cannot disagree. The era year for any date is computed from that table rather than looked up.
This site publishes era years from , the day Japan adopted the Gregorian calendar, and refuses to answer for earlier dates. Before that the official calendar was lunisolar: a Gregorian date in, say, 1870 does not map onto an era year without stating which conversion produced it, and giving a bare answer would hide that choice.
There have been more than 240 eras since 645 CE, many of them changed mid-reign in response to disasters or omens. Only the five of the modern period are listed here, because only from Meiji does one era correspond to one reign — the rule was fixed by the Imperial Household Law of 1889 and kept by the Era Name Act of 1979.
Reading an era year
To convert an era year to a Gregorian one, add the era's first Gregorian year and subtract one: Showa 40 is 1926 + 40 − 1 = 1965. The subtraction is there because the first year is year one and not year zero — the same reason a century runs from 01 to 00.
Era years still appear on Japanese driving licences, government forms, coins and newspapers, usually alongside the Gregorian year rather than instead of it.