Nov 4, 2009
How long does a U.S. patent last?
For a patent that issued before 6/8/95 (the date the General Agreement on Tariffs and Trade (GATT) became effective in the U.S.), the patent term is 17 years from the issue date or 20 years from the earliest effective filing date- whichever is longer.
For a patent that issues from a patent application filed on or after 6/8/95, the patent term is 20 years from the first effective filing date of the patent application.