Converting Japanese Era Years to Western Years: A Shōwa, Heisei and Reiwa Chart and Mental Math Tricks

Conversion formula and chart for each era

To convert a Japanese era year (wareki) to a Western year, you just add a fixed number for each era. If subtraction is easier to remember, subtract the same number to go from a Western year to an era year. First check the table.

In the other direction, from a Western year to an era year, subtract the same number. 1983 − 1925 = 58, so Shōwa 58; 2026 − 2018 = 8, so Reiwa 8. If memorizing the numbers is a chore, you can memorize one familiar year instead. If you know that Heisei 1 is 1989, Heisei 15 is 1989 + 15 − 1 = 2003. Don't forget to subtract 1 for the first year.

A mental-math trick using only the last two digits

Adding four-digit numbers like 1925 or 1988 isn't suited to mental math. In practice you only need to work with the last two digits, because the thousands and hundreds of the Western year barely change.

1. 1

   Remember the two digits to add for each era

   Shōwa is +25, Heisei +88 and Reiwa +18. Going further back, Taishō is +11 and Meiji +67. The eras you use day to day are Shōwa, Heisei and Reiwa, so remembering 25, 88 and 18 is enough.

2. 2

   Add it to the era year

   Shōwa 58: 58 + 25 = 83. Heisei 10: 10 + 88 = 98. Reiwa 8: 8 + 18 = 26.

3. 3

   If you pass 100, move up a century

   Under 100 means the 1900s; 100 or more means the 2000s. Heisei 31 is 31 + 88 = 119, so subtract 100 to get 2019. Reiwa 8 gives 26, and Reiwa is always in the 2000s, so 2026.

4. 4

   If you need the month and day, check the date the era changed

   For the year alone this is enough, but in a year when the era changed, the era depends on the month and day. Check the boundary years in the table in the next section.

For Shōwa, besides "add 25", it's useful to remember how long it lasted. Shōwa ran until 7 January of its 64th year, so a Shōwa year number never goes above 64. If you see something like "Shōwa 70", it's either a mistake or a hypothetical year counted as if Shōwa had continued (sometimes called Shōwa-equivalent counting).

In the year an era changes, two era years overlap

The years in which the era changed are where conversion most often goes wrong. One Western year contains two eras, so you can't fix the era year without looking at the month and day.

For example, someone born on 5 January 1989 was born in Shōwa 64, and someone born on 10 January was born in Heisei gannen. Same Western year, different era years. That's why one school year can include people born in Shōwa and in Heisei, and it's a common source of mismatches when checking documents.

These boundaries also matter when working out age from a date of birth. Japanese school years and the year you start school are divided at 1 April, so people born from January to March are one school year off from what the Western year would suggest. A tool that takes a date of birth and shows exact age and school year helps you avoid this kind of mix-up.

Rules for not mixing era and Western years in documents

In practice, the thing that causes more trouble than conversion itself is mixing era years and Western years within one document. It forces the reader to convert and leads to things being missed in checks.

• Keep one notation within a document: if you write your date of birth in Western years on a résumé, write your education and work history in Western years too. Mixing looks like a mistake by the writer.
• Follow any instructions: if the employer's or government office's form says "write in Western years", there's no need to rewrite in era years. If there's no instruction, either is fine.
• Use Western years as the basis for data entered into systems: handling era years as text in spreadsheets or ledgers makes sorting and calculating differences impossible. Store Western years and display era years only where needed.
• Avoid the era initials (S, H, R) in formal documents: shorthand like S58 works in internal notes, but in official documents the norm is to write Shōwa 58 in full.
• Use Western years for periods spanning an era change: for employment around 2019, "April 2019 – March 2020" is less likely to be misread than "April Heisei 31 – March Reiwa 2".

To check exact age from a date of birth, or how many days remain until a milestone, an automatic calculation is more reliable than doing it by hand. You can enter either a Western or an era date and get the age and elapsed days, so checking once before filling in a document lets you verify the numbers you write. Rules for consistent notation specifically on résumés, and how to work out the years for the education section, are in How to write years on a Japanese résumé; the etiquette for writing dates vertically, as on certificates or gift envelopes, is in How to write dates in vertical Japanese text. If you care about lucky and unlucky days (taian, butsumetsu) when choosing a date for a ceremony or taking delivery of a car, The meaning and order of the rokuyō explains how the sequence follows the old lunisolar calendar.

FAQ

How do I convert a Shōwa year to a Western year?

Add 1925 to the Shōwa year. Shōwa 58 is 58 + 1925 = 1983. For mental math, use only the last two digits: 58 + 25 = 83, so 1983. To go from a Western year to Shōwa, subtract 1925. Shōwa ran from 1926 to 7 January 1989, so the Shōwa year number goes up to 64.

In which Western year did Reiwa begin?

Reiwa gannen began on 1 May 2019. Within 2019, 1 January to 30 April is Heisei 31. To convert Reiwa to a Western year, add 2018 to the era year: Reiwa 8 is 8 + 2018 = 2026. A year in which the era changes contains two eras, so documents that include the full date need the month and day checked.

Should I write a Japanese résumé in era years or Western years?

Either is fine if there's no instruction. What matters is keeping it consistent within one document: if your date of birth is in Western years, write your education and work history in Western years too. If the employer's form says "write in Western years", or the era is pre-printed in the field, follow that. Avoid shorthand like S58 in formal documents.

Is someone born in 1989 a Shōwa or Heisei baby?

Those born from 1 to 7 January were born in Shōwa 64, and those born on 8 January or later in Heisei gannen. The era changed in 1989, so the Western year alone doesn't determine the era year. For the same reason, people born in 2019 are split into Heisei 31 (up to 30 April) and Reiwa gannen (from 1 May). When documents don't match, suspect this boundary first.