Hi RiyaR,

As David alluded to, performing at your best on Test Day is a matter of a number of variables (one of which is the time of day that you start your GMAT). Most Testing Centers offer 3 "shifts" of start times - a morning shift, an afternoon shift and an early evening shift. Since we're now in the busy time of the year (when many Test Takers are all attempting to schedule their Tests), you might have to schedule your exam a couple of months in advance if you want to take your GMAT on a specific day of the week and at a specific time.

One of your physical goals on Test Day should be to walk into the Test Center awake, alert and ready to perform at your best. Most Test Takers see a "drop off" in performance as the day goes on, so starting your GMAT at 5pm might be a problem (although it depends on when you wake up and the day's activities before the Test).

You can (and should) experiment a bit with your practice CATs - try taking them at different times of the day (but try to make the other aspects of those practice CATs as realistic as possible - take the entire CAT, in a Test-like setting, on a Desktop computer, etc.) and see how you perform.

GMAT assassins aren't born, they're made,
Rich