In May, Japan entered a new era, known as Reiwa, following the abdication of Emperor Akihito, and, consequently, ending the Heisei era. You may be asking, “What does this have to do with Japanese patent numbers?”, and these days the answer is “not much”, but that hasn’t always been the case.

Prior to 2000, the Japanese patent numbering system used the Emperor year (the number of years since the current Emperor ascended the Chrysanthemum Throne) as part of its numbering system to indicate the year in which various events occurred. The main events that affect those of us searching the Japanese patent database are the publication of patent or utility applications, and publication of the examined patent or utility applications.

The numbering format for these four publications is Yyy-nnnnnn, where Y refers to the Emperor era, yy refers to the Emperor year, and nnnnnn is a six-digit number.

Emperor eras relevant to us are Showa which ranges from 1926 to 1989, and Heisei which ranges from 1989 to 2019, although it is the period from 1989 to 2000 that is most of interest here.

Now things start getting a little more complicated, but stick with me. The numbering of years within each era restarts with each era, so 1926 is year one of the Showa era, or S01, and so on, up to 1989, which is S64. 1989 is also the first year of the Heisei era, so it’s also known as H01. 2000 is therefore H12, and H30 has just concluded.

One more thing, the six-digit number, nnnnnn, restarts each year at 000001, and the number for the unexamined application is different to the number for the equivalent examined application. What this means is, for a random number such as H01-066151, this could be the publication number for the unexamined or the examined application.

That’s generally fine within the Japanese system as it only takes one or two searches to find what you’re looking for, but here in the West we removed the Emperor era symbol, and we also took to removing, and I’m not sure it was consistent, some of the leading zeros within both the Emperor year, and the six-digit number. So the number above became JP 1066151. Is that H01-066151 or H10-066151? Is it examined or unexamined? Is it a clamp for a sofa or an antidepressant or even a piece of radio telephone equipment? Thankfully the European Patent Office realised there was a level of confusion, and now insist on the Emperor era as part of the number, although the leading zeros thing is still an issue. Many other sources of Japanese patent information haven’t made this leap.

After 2000, the numbering system moved to yyyy-nnnnnn, where yyyy is the Western year, and the application keeps this number until grant, regardless of where it is in the application process. It’s a much more straightforward system.

I also haven’t mentioned anything about granted patent numbers. They are numbered consecutively, regardless of a change in year or Emperor, although there have been a couple of jumps forward to a round number when the law changes. The last was to JP 2 500 000 in 1996 for patents.

What you need then, in order to locate older Japanese publications, is a sense of what the Emperor era is, a kind code such as A or U for an unexamined application or B or Y for an examined application, and an applicant name or an idea of the subject matter to help pinpoint the right one.

If not, there’s always this for afterwards.