Source : WordNet®

prime time
     n : the hours between 7 and 11 p.m. when the largest tv audience
         is available

Source : Free On-Line Dictionary of Computing

prime time
     
        (From TV programming) Normal high-usage hours on a
        {time-sharing} system; the day shift.  Avoidance of prime time
        was traditionally given as a major reason for {night mode}
        hacking.  The rise of the personal workstation has rendered
        this term, along with {time-sharing} itself, almost obsolete.
        The hackish tendency to late-night {hacking run}s has changed
        not a bit.
     
        [{Jargon File}]
     
        (1995-01-18)