<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Eugene:
Just keep in mind that the clock starts when your paperwork is processed at the counter, so calculate your timing accordingly.</font>
At least at Budget the one time I was in this situation, the start time of my rental was printed on my rental agreement.
I've heard that using the Hertz Gold service, your start time is when the driver calls in your name.