Seeing as how all 6 accounts (including CH) share the same Local Time, I would say that's a strong possibility.
It's the default (UTC). I bet vast majority of users never touched that setting and have the same time zone.
Having said that, I'm almost certain that all those users are you-know-who's alts, except Dig Bicks who showed up under different circumstances IIRC so that one is less likely.