This may be too simplistic as an explanation, but I've used it in helping novices understand the difference.
Timing is keeping the count on your steps.
Rhythm is moving your body properly to the steps and the accented beats, as Telemark describes.
If someone watching you dance says, "You've got good rhythm," they usually mean your body moved fluidly and nicely to the music. They are not going to say "You have good timing" when they compliment you.
I've always thought that the American style dances were called Smooth and Rhythm for a reason. The American Rhythm dances have the Latin motion and body movements used to the accented beats. Both styles have timing, but one has smooth movement, the other has rhythmic movement.
If I am way off on that analogy, someone who knows a lot more about dancing than I do would have to explain it better.
