Never. The interviewer needs to know that they can count on you to be at work by your assigned time every day. Start off by telling the interviewer that you are a punctual person, and you are always a couple of minutes early when arriving at work. Be sure to mention that you plan ahead for traffic, and if you live somewhere with snow, be sure to mention that you watch the weather ensuring you leave enough time to clean off your car and drive a little more cautiously when necessary. If you have children, be sure to mention that you have backup plans in place for childcare should something fall through with your typical plans.