I know this probably does not matter in the slightest, but I'm just curious.

Some people's join dates seemed to have moved forward by a day.

Why is this?

Have you considered that maybe they changed locations?
That could affect it since the place they moved to is a day ahead*Australia*

I don't think that would have any affect any since it would be based on where you first registered your account unlike your country code, which changes every time you log in (depending on your location). Also it's not just happened with one or two people, I've checked 5 profiles so far that have been affected by this.

Not sure though.

The servers have had their time/date changed a few times since + they've moved location half way across the world. That'll be why.

Alright, thanks.