There are three critical dates in the life of any patented invention:

(a) the date of invention; (b) the date of application for a patent; and (c) the date of issuance of the patent.

The first is important largely because of sec 102(a), which directs the PTO examiner to look at whether certain things were true prior to the date of invention (i.e. whether the invention was “known or used by others in this country” prior to date (a), etc.).

[Note: This is one of the places where the new patent law has significantly changed the landscape. Under the new law, the inquiry under §102(a) is whether the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention.” This apparently combines the §102(a) and §102(b) inquiries together, taking the filing date as the critical date for measuring whether the invention was in the prior art.]

The date of invention is also important because sec. 103 (as we’ll see) requires that patents be denied to any invention that was “obvious” at the date of invention.

The date of application for a patent is important largely because of sec. 102(b): Was the invention “patented in a foreign country,” or “in public use,” etc., in this country, more than one year prior to date (b)? [And, as noted above, the application date has become the critical trigger date for the revised §102(a) inquiry under the new patent law.]

Date (c) is important, because no patent rights attach to the invention prior to that date. Unlike copyright rights (which attach, you will recall, at the moment of “creation”), the exclusive rights that make up the bundle of patent rights do not come into being unless and until the duly authorized agency of the US government says they do (i.e., when the patent is issued). You can’t infringe rights that don’t yet exist; therefore, you can’t infringe a patent prior to date (c), because there are no exclusive rights prior to date (c).

Dates (b) and (c) are usually quite easy to ascertain. Not so with date (a); be on the lookout, as you read the various cases, for the ways in which courts define the date of invention.

During the interval between (b) and (c) – which, as we’ve mentioned, may be (and often is) several years long – the applicant is permitted to put “patent pending” or similar designations on goods distributed in the marketplace. [But see §292 of the Patent Act: “Whoever marks upon, or affixes to, or uses in advertising in connection with any article the words “patent applied for,” “patent pending,” or any word importing that an application for patent has been made, when no application for patent has been made, or if made, is not pending, for the purpose of deceiving the public, shall be fined not more than $500 for every such offense.”] The purpose of this designation is to alert members of the public that, while the article is not yet covered by patent rights (and therefore can be made or used by others without liability), it will possibly soon be the subject of such rights (and that there will be possible infringement liability at a later date for any such use of the article).