What does the priority date signify when filing patents?

The priority date in the context of patents is a crucial concept as it establishes the timeline from which the rights to the invention are measured. The correct answer indicates that the priority date refers to the date when a patent application is submitted. This date is significant because it determines the novelty of the invention and is used to assess whether the invention has been previously disclosed or used.

When filing a patent application, the priority date acts as a reference point that establishes the invention's protection timeline. If another party attempts to patent the same invention later, the priority date will determine which patent application is valid based on their filing dates. This is why it is essential for inventors to file their applications as soon as possible to secure their rights.

The other options address aspects related to patents but do not correctly represent what the priority date indicates. For instance, the date when a patent is granted relates to the completion of the examination process, while the date of the first public disclosure pertains to the public awareness of the invention. The idea of a grace period for filing for foreign protection is relevant to international patent laws but does not define the priority date itself. Thus, the understanding of the priority date is foundational in navigating the patent application process and ensuring the legal protection of inventions.