One needs to check several things before one can determine when
a patent will expire or has expired.
Determine the Patent term: First, you need to
determine the patent's filing date and whether it claims
priority to any earlier U.S. application. Most utility patents
today have a term that expires 20 years from the earliest filing of
the patent. However, patents that were pending at the USPTO before
June 8, 1995 are subject to a dual term that makes the patent term
the longer of: (1) 20 years from the patent's earliest
filing date, or (2) 17 years from the patent's issue date. For
example, if an application's earliest filing date is May 1,
1995, and it issued on May 1, 2000, the patent would be subject to
the dual term determination. The 20 year term calculation would
lead to an expiration date of May 1, 2015, but the 17 year from
issue term calculation would lead to an expiration date of May 1,
2017. Thus, the longer 17 year term from issue would apply. The
earliest
