[Jim Beltz]

You have all (for the most part) gotten the rule right, but here is where it gets better.

It is possible to start and stop a game clock with only one second showing on it in the situation described. The internal clock processor, even if the clock does not indicate 10ths/100th of seconds still processes them. What you don't know in a football game (I have never seen a fooball game clock show anything other that whole seconds)with .01 left on the clock is how close is .01 to .0001. The clock knows, but no one else does.

Now for the situation:

1. Clock shows .01 of time left
2. Snap is at the whistle (really quick center and almost simultaneous to whistle, but to some in the stands who are far enough away (insert sound distance travel time here) the snap was ahead of the whistle)).
3. Clock operator sees the snap, but he/she is a little slow in starting the clock, maybe caught off guard just a little by the quick snap. You could maybe add 2 or 3 tenths of a second here.
4. QB receives the snap and is really quick with his spike of the ball.
5. Clock operator who was slow to start the clock, and is now focused and trying to speed up almost anticipates the spike of the ball, and in so doing stops the clock absolutely instantaneously with the spike. Subtract 1 or 2 tenths here.
6. Everone looks up at the game clock and it hasn't moved. Do you hear the fans yet, or the other teams coach? At this point, maybe the white hat (with the last word on time) waives off the time and hoists the ball in the air...game over. NOW CAN YOU HERE THE FANS?

Point is, it would seem possible to get a play off and stop the clock without consuming one second even thought the clock was in fact started and stoped by the operator.