Short answer: a date of birth in yyyymmdd is 4-digit year + 2-digit month + 2-digit day, eight digits. April 7, 1990 is 19900407. If you only know the Japanese era year, convert it to the Western calendar first.
Examples
| Date of birth | yyyymmdd (8 digits) | yyyy/mm/dd |
|---|---|---|
| April 7, 1990 | 19900407 | 1990/04/07 |
| December 1, 2001 | 20011201 | 2001/12/01 |
| October 20, 1975 | 19751020 | 1975/10/20 |
| February 9, 2010 | 20100209 | 2010/02/09 |
Three rules: use half-width digits, pad a single-digit month or day with a leading zero, and do not add separators (unless the form asks for slashes, in which case follow the form).
What yyyy, mm and dd mean
| Symbol | Meaning | April 7, 1990 |
|---|---|---|
| yyyy | Year (4 digits) | 1990 |
| mm | Month (2 digits, 01–12): month, not minutes | 04 |
| dd | Day (2 digits, 01–31) | 07 |
In a date field, mm means "month". In a time field, mm means "minutes", so the meaning depends on whether the field is a date or a time.
Convert a Japanese era year to the Western calendar
Japanese forms often use eras. Add the following number to the era year to get the Western year.
| Era | Formula | Period |
|---|---|---|
| Showa | Showa year + 1925 | Dec 25, 1926 – Jan 7, 1989 |
| Heisei | Heisei year + 1988 | Jan 8, 1989 – Apr 30, 2019 |
| Reiwa | Reiwa year + 2018 | May 1, 2019 – |
| Era date | Western date | yyyymmdd |
|---|---|---|
| Showa 50, June 15 | June 15, 1975 | 19750615 |
| Showa 64, January 7 | January 7, 1989 | 19890107 |
| Heisei 1, January 8 | January 8, 1989 | 19890108 |
| Heisei 31, April 30 | April 30, 2019 | 20190430 |
| Reiwa 1, May 1 | May 1, 2019 | 20190501 |
In years when the era changes, the era depends on the date: through January 7, 1989 it is Showa, from January 8 it is Heisei. The first year of an era counts as year 1.
Why the input is rejected
- Full-width digits: "１９９００４０７" is often rejected. Switch to half-width.
- Separators included: do not add slashes or hyphens to an 8-digit field.
- Missing zero: April 7 is "0407", not "407".
- Era year left as is: something like "H02" must be converted to the Western year unless the form supports it.
- Wrong number of digits: count 8 (4 + 2 + 2). For a 6-digit field, see yymmdd.
Excel: make 8 digits and convert back
- Date to 8-digit text:
=TEXT(A1,"yyyymmdd") - 19900407 back to a date:
=DATE(LEFT(A1,4),MID(A1,5,2),RIGHT(A1,2)) - Convert a whole column: Data → Text to Columns → set the column format to Date (YMD).
For the meaning of yyyymmdd itself, see What is yyyymmdd?; for era conversion see Japanese era conversion.
Skip the typing
Entering dates in eight digits all day invites slips like "20260350". InsertDate is a Windows app that types today's date in yyyyMMdd when you press the Insert key. Enter other people's personal data such as dates of birth only through official forms, not through the app.
Frequently Asked Questions
How do I enter a date of birth in yyyymmdd format?
Write the 4-digit year, 2-digit month and 2-digit day with no separators. April 7, 1990 is 19900407. Pad single-digit months and days with a leading zero.
What does mm mean in a date of birth field?
In a date field, mm is the 2-digit month. In a time field, mm means minutes.
What Western year is Heisei 2?
Add 1988 to the Heisei year: Heisei 2 is 1990. Heisei began on January 8, 1989, so January 8 of 1990 or later falls in Heisei 2.
How do I convert a Reiwa date of birth to yyyymmdd?
Add 2018 to the Reiwa year. Reiwa 1, May 1 is May 1, 2019, which is 20190501.
Try InsertDate Free for 7 Days
Press Insert. Get today's date in yyyyMMdd. Works in almost any Windows app, including Excel, Word and Notepad, with no configuration. To type into an app running as administrator, run InsertDate as administrator too.
InsertDate is a Windows 10/11 app. Reading on a phone? Open this page on your PC to install it.