The rest of the world sets the patent priority date on the date of filing the patent. Only the U.S. has an regime that often leaves as a guess what a patent priority date might be, until it hits the fan in litigation. Patentees can swear behind prior art that gets in their way, claiming an earlier invention date than the day they filed for the patent. And, otherwise, it gets worse.

Patent holders in the U.S. get a grace period of one year with regard to prior art. What would be invalidating prior art in Britain, or other places in the world, doesn't count here in the land of freedom fries.

Title 35 U.S.C. § 102 & § 103 qualify anticipatory prior art. 102(a) & (b) most commonly apply. 102(a) disqualifies if "the invention was known or used by others in this country, or patented or described in a printed publication in this or a foreign country, before the invention," potentially leaving the date to guesswork with our U.S. first-to-invent scheme. 102(e) is also "before the invention." 102(b), with "the invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country, more than one year prior to the date of the application for patent in the United States," grants a grace period of a year prior to the filing date. This makes a farce of the concept of first-to-invent. 102(c),(d), (f), and (g) don't often apply.

103(a) is the most commonly applied of that section, used for a stretch as to what "would have been obvious at the time the invention was made to a person having ordinary skill in the art to which said subject matter pertains." Tell it to the jury; see if they, not likely to be "skilled in the art", can make sense of the advanced technology before the other side makes the fog roll in with confounding expert witness testimony. The ribbing aside, 103(a), though arguably too vague in specifying what constitutes obviousness, is a necessity to avoid patenting obvious combinations.

Patent reform is theoretically on the radar screen of Congress, but actual legislation coming out of the hopper is as likely in this election year as you winning the lotto.

Most important, there has been no serious legislative consideration to eliminating the one-year grace period. The now deceased H.R. 2795, the Patent Reform Act of 2005, went for international harmonization with a first-to-file regime, but left 102 with "more than one year before the effective filing date of the claimed invention".