I want to do a free state of the art patent search and I wan to know, how far do I have to go back in time to be 100% sure all shown patent documents are free state of the art? Up until now I was looking at patent documents that have a priority date at least 20 years + 18 months back, do I have to go even further back in time?

2 Answers 2


Be advised that in the US, at least, there is the possibility of "patent term adjustments". Basically this is an add on the term to make up for excessive length of time in the patent approval process.

As for free searching, Google Patents and especially Lens are excellent sites. That said, if you find an important patent, I would look it up in the issuing country's system to get the most accurate and thorough information.


The state of the art usually means the current state based on the very latest publications. You are looking for the free-to-use state which is not the actual state of the art.

In most of the world the term of invention patents is and has been 20 years from application filing. There are other, shorter, terms for other things like utility models, plant patents and design patents where they exist.

The term of US patents changed for applications filed after June 7, 1995. It is now 20 years from filing. For applications filed before that date it is 17 years from grant.

There are still some application pending from that earlier era and when/if they issue the term will be 20 years from issue. For patents filed since June 7, 1995 there is the possibility of patent term extension beyond the 20 years based on delays caused by the patent office.

For pharmaceuticals there is a different extension based on the FDA approval process.

So you need to measure some patents from application date and others based on issue date. If you want to add a factor for patent term extension you could look at both filing and issue dates since the extension scheme is motivated by an estimate of a three year pendency so the new 17 years approximates the old 20 years.

I don’t have any suggestions for pharmaceutical patent term extensions.

  • Are there any guides on how to perform free-to-use state patent searches, since I cannot find any? Commented Feb 12, 2023 at 9:04
  • In Germany the term "state of the art" or in german "Stand der Technik" describes all inventions of to a specific point of time. This means, that not only all the new ones count as state of the art, but also all that came before that, like described here by IHK, a german institution: ihk.de/freiburg/innovation/produktentwicklung/…". This info is for everyone that may look for this in the future and come to this page. Commented Feb 12, 2023 at 16:36
  • I agree that state of the art includes everything up to a certain time.
    – George White
    Commented Feb 12, 2023 at 17:38
  • Yes, see the Lens lens.org, a very good free site. They do have number of cites in the results but I think not to search on. Within a class that shouldn't be a problem.T here are guides adn tutorial videos. I think there is a paid version but I have just tried that feature on the free version. See my answer.
    – George White
    Commented Feb 13, 2023 at 5:54
  • I suggest you getting your information straight from the source. Deutsches Patent- und Markenamt: dpma.de or European Patent Office: epo.org
    – picibucor
    Commented Feb 13, 2023 at 9:57

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