Explore our expert guide to patent filing in Chicago. Get practical tips and essential insights to protect your innovations effectively.A priority date patent establishes the priority date as the earliest date an application may claim precedence. 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. If you only have one application, the filing date is the same date as the priority date. The priority date is the earliest date to which a patent application can claim priority. Patent applications publish 18 months after the priority date. Labeled Patent or Application Number. Place. Office. The filing date is the date when a patent application is first filed at a patent office. The priority date, sometimes called the "effective filing date",