I believe there may be a problem with the "Edited by..." label.
I recently edited a post in the Systems forum and the edited time is listed as approximately 2AM 5/19/11. Here on Pacific time it was 5PM 5/18/11. That would mean that the time should read (I'm guessing) 8PM 5/18/11 (Eastern time). The posting times are fine as far as I can tell, I'll have to see if this persists with the editing time though. Hopefully this helps.
I took the screenshot shortly after at 5:30 5/18/11 (PDT), that's why the times don't exactly agree.
I think it has more to do with the software and not a "bug". The "home system" is out of France (BestOfMedia) which would reflect the correct time there. I have seen this many times before, so I wouldn't worry too much... IMO