The entire process from the date of submission to obtaining the Letters of Patent could take up to one year. Deadline. For clients claiming priority i.e.Filed application for patent filed in the United States may claim the benefit of, or priority to, a prior application filed in the United States. The priority date determines whether another patent filing or publicly available document qualifies as prior art against one's patent application. What is a patent priority date? Priority date refers to the earliest filing date in a family of patent applications. An application for patent filed in the United States may be entitled to the benefit of the filing date of a prior application filed in a foreign country. A priority claim is made to an earlierfiled patent application. For example, an Applicant can claim priority in a later-filed patent application.