How do you calculate the life span of patents? calculation of the life span of patents starts from the date on which you the patent application.

A patent term is the maximum amount of time during which a patent can be maintained in force. Normally, it is expressed in a number of years either beginning from the date of grant or the filing of the patent. Example is a US utility patent which is usually granted for twenty years from the date the patent application is filed or granted

this seems to be in the wrong category. but i'll take some free points my dude

posting this in wrong category will result in people seeing it who won't know the answer.