how long us patent
How long a patent lasts depends on when the application was filed with the U.S. Patent and Trademark Office. For U.S. patents filed through June 17, 1995, the patent lasts for 17 years from the date the patent is issued, provided that the fees necessary to keep the patent in force (maintenance fees) are paid. For patent applications filed after June 17, 1995, the patent last 20 years from the date of filing. Since applications typically take one to three years to process, most patents filed after 1995 have an effective duration of 17-19 years.