The change came in CFR 14 Part 29 amendment 39.
Part 29 is the Certification standard for large rotorcraft (and CS29 the EASA equivelant), and it includes the requirements for Cat A performance. Eralier amendment referred to CDP and from 39 onwards TDP. From Joe line pilot's perspective, no difference!
If you want to read more, look up Part 29 and also AC29-2C (just google, with FAA thrown in to narrow it down)