Bean says time can't have momentum. but I'll take it one step farther:

"When is 'now'? Saying that 'now' is 'this instant' is going around in circles. Every instant is 'now' when it 'happens.' The point is, how do you measure the rate of moving from one instant to the next? And the answer is, you can't. What's the rate of the passage of time?''
-Gregory Benford, Timescape

well, let's see... time passes at exactly one second per second....