That local time thing only estimates where the signal is coming from. Mine said Limerick, Ireland. That's where your ISP is based. Given that I live 200 miles from Limerick... eh yeah. It's an independent tool. That's not how they determine if you're a multi or not.

Okay, I will admit that yes, PhBB moderator tools are pretty crap. But, there are add on tools available to make it better and I am sure that they have those installed for admins. The advantage to forum softwares like PhBB are that you can manipulate the styles to however you want them. Some of the softwares with better tools are pretty rigid code wise, meaning that you will have a hard time manipulating styles to how you want.
With certain softwares you can pretty much find anyone with a certain IP from the mod panel with one click and then all the IPs associate with those accounts and then with a level 2 search, anyone else who shares one or more of the IPs with any of those accounts. Okay, from post patterns you can tell who just shares a dynamic IP or whatever. Pretty cool, eh? It's a lot easier to spot a multi than you think.