Today for example: I'm scheduled to work 2-9pm. You don't necessarily have to clock out for the lunch hour at the time posted on the schedule, you can go a bit earlier if you're caught up on stuff, or you can go later, just not over 6 hours later, you'd get a write-up for that. If I clock in at 2:00, wait till 8:00 to go to lunch, and I'm only scheduled till 9:00, I can just go ahead and go home. Nothing "illegal" about that, already asked some co-workers that have worked there several years.
Just need to eat a decent amount before leaving the house today!