4 outside bulbs come on at 10:30am
4 inside bulbs come on at 11:00am
Inside bulbs off again at 10:30pm
Outside bulbs off again at 11:00pm
So I guess 12.5 hours
But I should mention, my lights are also programmed to turn off between 3:30-4:30pm (considering making it 5:30pm). Part of an experiment to reduce algae growth/disrupting its photosynthetic cycle.