Typically the internal clock will allow the user to wake up with very little drowsiness.
To set the internal clock the user must think of the time for at least 3 seconds. Results vary per person.
*Note: if user ignores his internal clock and goes back to sleep they may be more tired than normal when waking up. Not Suggested!
Guy: Don't worry just set your internal clock tonight.
User: Worked like a charm. Why do people waste money on alarm clocks.
Guy: Told ya so