Русско-англо-русский юридический словарь

Since the patent term (35 U.S.C. 154) would expire on ___, the period of extension is the number of days to extend the term of the patent from its expiration date to and including ___, or ___ days. (Official website of the United States Patent and Trademark Office)

A permanent contract (also called indefinite contract) is a contract with no expiration date, which remains valid until either employer or employee chooses to end the agreement. (UNESCO UIS)