People always try to end meetings five or ten minutes before the top of the hour, and it never works. If I see a “20 minute” meeting scheduled to end at 2:50pm, I know it’s ending at 3:00pm.
So if you want a short meeting, don’t end early. Start late. Schedule a meeting from 2:40-3:00pm and that sucker will last 20 minutes guaranteed.
(Or better yet, don’t have the meeting at all.)