This chart sets out the effective dates for key US patent law reforms under the Leahy-Smith America Invents Act (AIA) enacted on September 16, 2011. It identifies changes that became immediately effective on that date including the changes concerning the prior commercial use defense, the best mode defense, patent marking and litigation procedure. It also identifies other subsequent changes, including the first-inventor-to-file system, changes to the definition of prior art, the creation of derivation proceedings, post-grant and inter partes review, supplemental examination, pre-issuance submissions and changes to the use of advice of counsel in defending against a charge of willful infringement.