Cavediver points out that there was a point of T=0. We don't know why the clock started ticking.
Uh-oh, no clock started ticking at T=0. How do I explain this at 00:45 in the morning...
Back to my globe analogy
North Pole is the Big Bang (last time it may have been south pole but hey...) What you and I think of as moving through time is moving downwards parallel to the Earth's axis. You have to move quite a way (south) from the North Pole before you begin to experience time, i.e. start moving down rather than across.
In other words, clock ticking time is only a real feature of the universe away from the Big Bang. Close to it, things just are.
Actually, time is really only a consequence of conciousness, and vice-versa... but that's for another day