Under FARs, a "Safety Pilot" can log time as P1. This is only applicable if the captain is wearing foggles and flying on instruments in VMC - if that's the case, both he and the person sitting next to him can log the time, and count it towards any hours that the FAA may require.
Under JARs, the best a Safety Pilot can do is log the time as "Supernumary". You write "SNY" in the Holders Operating Capacity column in your logbook, and the time itself does not count towards anything at all, including your total time. This is all described in LASORS.
If you are applying for JAR licenses or ratings, you must use JAR rules, regardless of where you actually did your flying.
FFF
--------------