A patent is only in force during its term and in its jurisdiction. When the patent term runs out, or if it is abandoned or invalidated in a particular jurisdiction, unless there is a continuation in force, the matter in the patent enters the public domain. See also What determines a patent's in-force duration?
For utility patents issued in the USA:
- If the application from which the patent issued was filed on or after June 8, 1995, the patent term begins on the patent issue date and ends 20 years after the effective filing date of the application. Not the day before (though probably few would want to go to court about conduct occurring on 11:59 PM that last day).
- If the application is a continuation, continuation-in-part or division of a prior application, then its effective filing date is the filing date of the earliest filed non-provisional application in the chain of applications.
- Remember, if the earliest application filed was a provisional application, that filing date does not count as the earliest date. This is also true for non-US applications, so look out for Australian or other provisional filings which serve as the priority documents when you do your patent term calculations.
- If the application from which the patent issued was filed before June 8, 1995, the term of the patent is the longer of: (a) 17 years from issue date, or (b) 20 years from effective filing date.
- A tricky case: If the application is the U.S. national stage of an international application filed in the PCT system, then its effective filing date is the international filing date despite the fact that the PCT application might have claimed priority to an earlier application. How can you identify such a patent? The face of the patent and/or the first paragraph of the specification should indicate that the application was filed under 35 USC 371.
Check out this cool website http://www.ssjr.com/tools/toolshell.aspx?tl=1 which will calculate a US patent term for you (but the catch is you have to fill in the correct effective filing date, bearing in mind the facts above).
For some examples for the US, see the table in http://en.wikipedia.org/wiki/Term_of_patent_in_the_United_States and see whether you get the same answers.
For patents issued in Europe:
Generally, the term of a patent, which must be registered in an EU country in which it is to be enforced, is 20 years from the earliest effective priority date as per the TRIPS agreement. There's a special case where an application filed under the PCT enters the EPO, but remember not every patent application filed in the EPO is filed under the PCT.
However, when an application filed under the PCT is filed in the EPO as it enters its regional phase, the term is 20 years from the international filing date.
For patents issued in Canada:
For patent applications filed before October 1, 1989, the term of the patent is normally 17 years from the date of issue. However, where the term for the patent had not expired before July 12, 2001, then the term is 17 years from the issued date or 20 years from the filing date, whichever term expires later.
For patent applications filed on or after October 1, 1989, the term of the patent is 20 years from the date of filing of the application. See the Canadian Intellectual Property Office website.
For patents issued in other countries:
Most countries that have had different rules in the past are now harmonizing on 20 years from the earliest effective priority date, as per the TRIPS agreement. Some countries have special extensions, e.g. in Brazil there is a minimum term guaranteed, and in the US there can be patent term adjustments associated with delays while the patent application was being examined. See the pages on each country.
Different Flavors of Patents
Some jurisdictions grant patents after little or no examination. Substantive examination of whether the patent claims are actually valid may occur during a litigation.
Utility Model Patents: (not to be confused with "Utility Patents", i.e. what most people think of as "patents"). These have a term of ten years from the filing date. Generally EU countries offer this option, as do Bulgaria and China. In Japan, Utility Model Patents have a term of six years from the filing date.
Simple Patents: Granted in Indonesia, these patents have a term of ten years and so are similar to Utility Model Patents.
Petty Patents: Australian petty patents, which were abolished in 2001, have a term lasting for six years from the filing date. Thailand still grants petty patents, also valid six years from the filing date.
Innovation Patents: These patents, in Australia, replace the petty patent. Their term lasts for eight years from the filing date.
Design Patents: 14 years from the date of issuance in the USA. The rules vary in some other countries.
This is not an exhaustive list of the different types of patent applications.
How can you tell what kind of patent you’re dealing with?
You need to check the INPADOC codes. These are updated occasionally, so the best place to check if you are uncertain is http://ep.espacenet.com/