The U.S. has a grace period of one year from publication, sale, or offer for sale. Under 35 U.S.C. 102 (b), prior art includes publications that were published more than one year before the priority date of the patent application.

The grace period is a bit misleading, though. The U.S. PTO doesn't just just care about dates of publication, it cares about dates of invention. Under 35 U.S.C. 102 (a), prior art includes publications that were published before the date of invention. Of course, since the Examiner doesn't know the date you invented, he/she assumes that date is the filing date. You can pre-date the publication by submitting a Declaration under 1.131 demonstrating invention before the publication date.

The U.S. also cares about the filing of applications by others. Under 35 U.S.C. 102 (e), a patent application by another that discloses, but does not claim, the same subject matter, can be prior art if the application was FILED (not even publicly available) before the date of invention. Such art can similarly be overcome by filing a Declaration under 1.131.

102(b) is an absolute bar that can not be sworn behind, and applies to art of another as well as the invnetor/inventive entity. 102(e) applies to the art of another and can be sworn behind, in order to disqualify it as a reference.

102(e) art are patents or patent publications filed by another before your file date but published later. Sec. 102(a) and (b) art are disclosures made public before your file date. Sec. 102(e) is a novelty bar enforcing the US first to invent system. If the invention was described in a published U.S. or PCT patent application, filed by another person prior to the date of invention, then the bar applies. This follows from the US first to invent principle: A description of the invention by another prior the date of the second inventors “invention” is obviously predating the second inventor and creates the bar. In Europe, there is a similar bar but it applies from the date of filing (EPC, art 54(2)). See also MPEP 706.02(a).