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Q: Determining expiration dates of US patent ( Answered 5 out of 5 stars,   1 Comment )
Subject: Determining expiration dates of US patent
Category: Relationships and Society > Law
Asked by: dan89-ga
List Price: $4.00
Posted: 21 Apr 2002 01:19 PDT
Expires: 28 Apr 2002 01:19 PDT
Question ID: 2434
(1) How do we determine the expiration date of a US patent?  It used to be 17 
years from issue, and is now 20 years from the filing date.  I need a clear-cut 
formula, and a legal reference (e.g., the Manual of Patent Examining Procedure -
 MPEP) to support it.  For example, "any patent filed before mm/dd/yy will 
expire on ..., patents filed after mm/dd/yy will expire..."
(2) Is there a best-of-both-world clause, whereby a patentee would get to 
choose the later of two expiration dates? (need reference)
(3) When determining filing dates, is the question based on the actual US 
filing date, or is it based on the application's earliest priority date? (need 
Subject: Re: Determining expiration dates of US patent
Answered By: cindy-ga on 21 Apr 2002 19:59 PDT
Rated:5 out of 5 stars

Thanks for your inquiry.  I was able to find quite a bit of information about 
the changes in patent expiration dates, and so will give a quick summary 
followed by a more detailed look at references.

Because of recent changes in the law, an existing patent can fall in one of 
three categories in terms of its expiration date.  If the patent application 
was filed after June 7, 1995, the expiration date is 20 years from the date it 
was filed.  If the application was filed by June 7, 1995 and issued before June 
8, 1978, the expiration date is 17 years from issuance. The “best-of-both-
worlds clause” comes into effect if the application was filed by June 7, 1995 
and issued after June 7, 1978, in which case the term is the later of 17 years 
from issuance or 20 years from filing.  These terms are accurate for both 
Utility and Plant Patents, Design Patents expire 14 years from the date of 

This information was found at:

(URL courtesy of Drmatt’s Comment).


How the filing date is determined depends on whether the application is for a 
provisional or non-provisional patent.  For a provisional patent application:

“The filing date of a provisional application is the date on which a written 
description of the invention, drawings if necessary, and the name of the 
inventor(s) are received in the USPTO. To be complete, a provisional 
application must also include the filing fee, and a cover sheet specifying that 
the application is a provisional application for patent. The applicant would 
then have up to 12 months to file a non-provisional application for patent as 
described above.”

and for a non-provisional patent application:

“The filing date of an application for patent is the date on which a 
specification (including at least one claim) and any drawings necessary to 
understand the subject matter sought to be patented are received in the USPTO; 
or the date on which the last part completing the application is received in 
the case of a previously incomplete or defective application.”

For more information about the change in patent terms, see:

Information about extending or adjusting the expiration date of a patent can be 
found at:

In addition, Micropatent provides information on patent terms that agrees with 
the above information and includes references to the appropriate sections of 
the law.

“Patents will Expire as Follows:
(1) The term of any utility or plant patent that is in force on or results from 
an application filed before June 8, 1995 is the greater of the 20 year term 
provided in 35 U.S.C. 154(a)(2) or 17 years from grant subject to any terminal 
disclaimers. 35 U.S.C. 154(c)(1).
(2) All utility and plant patents granted on applications having an actual 
United States filing date on or after June 8, 1995 are granted for a term which 
begins on the date on which the patent is granted and ends 20 years from the 
date on which the application was filed in the United States. If the 
application contains a specific reference to an earlier application under 35 
U.S.C. 120, 121 or 365(c), the patent term ends twenty years from that date on 
which the earliest application was filed. 35 U.S.C. 154(a)(2).
(3) All design patents are granted for a term of 14 years from the date of the 
grant. However, the term of any patent may have been curtailed by disclaimer 
under the provisions of 35 U.S.C. 153, have lapsed due to failure to pay 
maintenance fees, or have been extended under the provisions of 35 U.S.C. 154, 
155, or 156. Thus, if more reliable information is needed with respect to a 
particular patent, then the specific patent file should be reviewed to 
determine the actual date of patent expiration.”

A copy of  the Patent Act (35 U.S.C.) referred to in the above quote can be 
found on the website of the United States Patent and Trademark Office at:

Listed below are the applicable sections of both relevant Codes:

From United States Code Title 35 – Patents
35 U.S.C. 120
35 U.S.C. 121
35 U.S.C. 135(a)
35 U.S.C. 154(a)(2) – 20 year term definition
35 U.S.C. 154(b) – extending/adjusting a patent expiration date
35 U.S.C. 154(b)(1)(A)
35 U.S.C. 154(b)(1)(B)
35 U.S.C. 154(b)(2)(C)
35 U.S.C. 181
35 U.S.C. 365(c)

From Title 37 – Code of Federal Regulations Patents, Trademarks, and Copyrights
37 CFR 1.701
37 CFR 1.702 – 1.705
37 CFR 1.702(a)-(e) and 1.703(a)-(e)
37 CFR 1.705

Some reference URLs:
The United States Patent and Trademark Office

“General Information Concerning Patents” from the USPTO

‘Lectric Law Library

Micropatent, general patent information

Search terms used:
patent expiration "17 years" "20 years"
1994 amend OR amendment patent law GATT
u.s. patent office


Request for Answer Clarification by dan89-ga on 21 Apr 2002 23:35 PDT
Great answer, again, but can I assume that the date you wrote twice in the 
first substantive paragraph "June 8, 1978" should have read "June 8, 1998"?

Clarification of Answer by cindy-ga on 22 Apr 2002 09:38 PDT

Thanks for the feedback.  

Actually, I think 1978 would be the correct year.  If the patent was filed 
before June 7, 1995 and issued before June 8, 1978 then it would have expired 
by the time the new law took effect, and so would not be included in the 
retroactive term increase.  Perhaps it would be simpler to say that all active 
patents at the time of the new law were included in the “20 years from 
application OR 17 years from issuance” whereas all subsequent patents were 
given a term of 20 years from date of application.  

Let me know if you have any other questions, or if you still think I’m reading 
this incorrectly.

dan89-ga rated this answer:5 out of 5 stars
Thanks, cindy-ga.  That was exactly what I needed.

Subject: Re: Determining expiration dates of US patent
From: drmatt-ga on 21 Apr 2002 12:29 PDT
I think the information at
answers at least part of your question.
It says for patents filed after 1995:
" If a U.S. Patent Application is filed after June 7, 1995, then 
the patent expires 20 years from filing of application."

These seem to be good book about patent laws:
Patent Law Essentials : A Concise Guide

Patents and How to Get One : A Practical Handbook

Patent law information can be found at the following sites:

Hope that helps.

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