Might be closer to tech-support, but I know the answer so I'll answer.

Welcome to qhimm's forums, by the way.
I don't know technical details on WHY this happens, but it ALWAYS happens when you're running a multi-core processor system and more than one core is running the game. You have two choices:
1) set the game to run on a single core and the time will run normally
2) enjoy the additional time you get as this applies to ALL timed events

That's about all there is to it.