Hello, me again, with my timezone issues (he he).
I found another website that tries to detect your timezone:
It says the following: "TZ" : "EDT", "TZOFFSET" : "-14400"
To see this you have to open up the source page (CTRL+U) and search for TZ
It's like Firefox is reporting a bad timezone to the requesting website regardless of wether torbutton is on or off.
Looks like no one is around, I'll check back tomorrow, bye.