I run mine from 7:30am to 7:30pm. They ramp up and down for two and a half hours, so 7 hours of full intensity. No moon lights, completely dark for 12 hours.
I suggest doing times when you look at your tank more often. If you are home more at night, I suggest 12pm-9pm. Or if you like to look at tank in the morning, 9am-6pm. Ramping the lights up and down for the first and last hour replicates sunrise/sunset in the ocean.