Patent term adjustment

In the United States, under current patent law, the term of patent, provided that maintenance fees are paid on time, are:

The patent term in the United States was changed in 1995 to bring U.S. patent law into conformity with the World Trade Organization's Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPs) as negotiated in the Uruguay Round. As a side effect, it is no longer possible to maintain submarine patents in the U.S., since the patent term now depends on the priority date, not the issue date.

Design patents have a shorter term than utility patents. Design patents filed on or after May 13, 2015 have a term of 15 years from issuance. Design patents filed prior to May 13, 2015 have a term of 14 years from issuance.

The original patent term under the 1790 Patent Act was decided individually for each patent, but "not exceeding fourteen years". The 1836 Patent Act (5 Stat. 117, 119, 5) provided (in addition to the fourteen-year term) an extension "for the term of seven years from and after the expiration of the first term" in certain circumstances. In 1861 the seven-year extension was eliminated and the term changed to seventeen years (12 Stat. 246, 248). The signing of the 1994 Uruguay Round Agreements Act then changed the patent term from seventeen years from the date of issue to the current twenty years from the earliest filing date.

If the United States Patent and Trademark Office fails to examine a patent application in time (deadlines for various steps are different), the patent term may be extended. Extensions or other delay taken by the applicant can reduce or eliminate the extension.

...
Wikipedia