37 CFR 1.109 : Patents, Trademarks, And Copyrights (§ 1.1 To Chapter V) — (§ 1.1 To Chapter V) — United States Patent And Trademark Office, Department Of Commerce (§ 1.1 To Parts 151-199) — General (§ 1.1 To §§ 5.31-5.33) — Rules Of Practice In Patent Cases (§ 1.1 To § 1.1071) — National Processing Provisions (§ 1.31 To § 1.378) — Examination Of Applications (§ 1.101 To § 1.110) — Effective filing date of a claimed invention under the Leahy-Smith America Invents Act.

(a) The effective filing date for a claimed invention in a patent or application for patent, other than in a reissue application or reissued patent, is the earliest of:

(1) The actual filing date of the patent or the application for the patent containing a claim to the invention; or

(2) The filing date of the earliest application for which the patent or application is entitled, as to such invention, to a right of priority or the benefit of an earlier filing date under 35 U.S.C. 119, 120, 121, 365, or 386.

(b) The effective filing date for a claimed invention in a reissue application or a reissued patent is determined by deeming the claim to the invention to have been contained in the patent for which reissue was sought.