Priority date

The priority date is the earliest filing date claimed by a patent application. It is the legal cut-off used to assess novelty and inventive step: anything published before the priority date counts as prior art against the application. Most national and regional patent systems allow an applicant to claim priority from an earlier filing — typically a first application in another country — for up to twelve months under the Paris Convention. The priority date is distinct from the actual filing date and from the publication date. Knowing the correct priority date is essential when evaluating freedom to operate or assessing the strength of a patent.