A Japanese form asks for your birthday in Showa years. An old document mentions Heisei 15 and you need the Gregorian year. Japan’s era (wareki) system confuses newcomers and natives alike — mostly because eras change mid-year and the first year is written as “gannen” instead of “1”.
This guide explains the one formula that converts era years to Gregorian years and back, provides charts for Reiwa, Heisei and Showa, and covers the transition years where the exact date matters. A free browser converter resolves everything, including boundary dates, at the end.
The Conversion Formula
Converting an era year to a Gregorian year takes one line:
Gregorian year = era start year + era year − 1
For example, Reiwa 6 is 2019 + 6 − 1 = 2024. Going the other way, subtract one less than the start year: era year = Gregorian year − (start year − 1). The “−1” exists because the first year of an era is counted as year 1, not year 0.
What "gannen" means: The first year of an era is traditionally written as "gannen" (year one) rather than with a number. Reiwa gannen is 2019, Heisei gannen is 1989, and Showa gannen is 1926. "Reiwa 1" means the same thing, but official forms usually prefer "gannen".
The Five Eras at a Glance
Modern Japan has used five era names:
| Era | Gregorian span | Era years |
|---|---|---|
| Meiji | 1868–1912 | Meiji 1–45 |
| Taisho | 1912–1926 | Taisho 1–15 |
| Showa | 1926–1989 | Showa 1–64 |
| Heisei | 1989–2019 | Heisei 1–31 |
| Reiwa | 2019– | Reiwa 1– |
Reiwa Chart
| Era year | Gregorian |
|---|---|
| Reiwa 1 (gannen) | 2019 |
| Reiwa 2 | 2020 |
| Reiwa 3 | 2021 |
| Reiwa 4 | 2022 |
| Reiwa 5 | 2023 |
| Reiwa 6 | 2024 |
| Reiwa 7 | 2025 |
| Reiwa 8 | 2026 |
Because the formula is “era year + 2018” for Reiwa, you can convert by simple addition once you remember the start year.
Key Heisei and Showa Years
| Era year | Gregorian | Era year | Gregorian |
|---|---|---|---|
| Heisei 1 | 1989 | Showa 30 | 1955 |
| Heisei 5 | 1993 | Showa 40 | 1965 |
| Heisei 10 | 1998 | Showa 50 | 1975 |
| Heisei 20 | 2008 | Showa 60 | 1985 |
| Heisei 31 | 2019 | Showa 64 | 1989 |
For everyday purposes you only really need three start years — Showa 1926, Heisei 1989, Reiwa 2019. Add the era year after subtracting one: Heisei 20 is 1988 + 20 = 2008; Reiwa 3 is 2018 + 3 = 2021.
Transition Years — Where the Date Matters
Eras change on the day a new emperor ascends, so some Gregorian years contain two era names. There have been four such transitions in the modern system:
| Transition | Through | From |
|---|---|---|
| July 30, 1912 | Meiji 45 | Taisho 1 |
| December 25, 1926 | Taisho 15 | Showa 1 |
| January 7, 1989 | Showa 64 | Heisei 1 |
| April 30, 2019 | Heisei 31 | Reiwa 1 |
So 1989 was Showa 64 until January 7 and Heisei 1 from January 8. When someone says they were “born in 1989”, their era depends on their birthday — which is exactly why the “Gregorian to era” direction needs the full date.
Concretely: someone born on January 5, 1989 was born in Showa 64; someone born ten days later was born in Heisei 1. When restyling a resume from Gregorian to era years, check whether any of your dates fall in a transition year — those are precisely the spots where memory and paperwork drift apart.
The notation of the first year also varies by document. Handwritten official forms use “gannen” (Reiwa gannen), while systems and web forms often expect a number — “Reiwa 1” or “R1”. All three mean the same year, so follow whatever format the form asks for.
One more caveat: this formula applies to the Gregorian calendar, which Japan adopted in 1873 (Meiji 6). Dates before Meiji 1 (September 8, 1868) ran on the old lunar calendar and need historical sources rather than arithmetic.
Convert with a Tool
When mental math is inconvenient, the Tools Hub wareki converter converts in both directions — era to Gregorian and Gregorian to era — and its Gregorian mode takes a full date, resolving transition years exactly. The conversion runs entirely in your browser and nothing you enter is transmitted.
How to use it (3 steps)
Pick a direction
Choose the era-to-Gregorian tab or the Gregorian-to-era tab.
Enter the era year or the date
Select an era and enter its year, or type a Gregorian date. Transition years are judged by the exact date.
Read the result
The Gregorian year, or the era with gannen notation, appears instantly.
Tool mentioned in this article
Japanese Era (Wareki) Converter
Two-way conversion with exact era boundaries. In your browser, free, no sign-up.
To turn an era-date birthday into a current age, use the age calculator; for the days remaining until a deadline, the date calculator works the same way.
Summary
- The formula is Gregorian year = era start year + era year − 1
- The first year of an era is written “gannen” (Reiwa gannen = 2019)
- Transition years contain two eras — check the exact date (1989, 2019 and others)
- The formula applies from Meiji 1 (September 8, 1868), when Japan adopted the Gregorian calendar
- Tools Hub’s wareki converter handles boundary dates automatically, free in the browser
Before filling in a form, glance at the chart or run the tool once — era-entry mistakes are entirely preventable.
FAQ
What Gregorian year did Reiwa start in?
Reiwa began on May 1, 2019. Reiwa 1 (gannen) is 2019, and 2026 is Reiwa 8.
Is 1989 Showa or Heisei?
Both — Showa 64 ran through January 7, and Heisei 1 began on January 8. Confirm the exact date whenever a transition year is involved.
What does “gannen” mean?
It is the traditional notation for the first year of an era: Reiwa gannen is 2019, Heisei gannen is 1989, and Showa gannen is 1926. It is equivalent to era year 1.
Can I convert years before Meiji (the Edo period)?
This guide and the tool cover Meiji 1 (September 8, 1868) onward. Earlier dates used the old lunar calendar, so simple arithmetic does not apply — consult historical sources instead.
