I Hate My Boss

If you are punching in then arriving ten minutes early is moot. He has no right to demand that you pitch ten minutes early if he isn't going to be there to allow you in. He's stealing your time. Do you have some kind of documentation that states what time you officially start? If so then make him stick to it. Get there a minute early every day next week and punch in on time, and if he bitches then tell him that you are well within your rights as per your terms of employment. If he doesn't like that then ask him how he would feel if the shoe was on the other foot. You are perfectly within your rights to expect an explanation, after all you are not a slave!