Mine are in the family room, which is in our basement, so they get light in a somewhat inconstant pattern (I'm usually home in the daytime since I work from home, but I do go out sometimes in the afternoon when my work is done, in which case I do turn off the lights. We have small bay windows, so it is not pitch black during the daytime even with the lights out, but it is definitely dark.) Plus I'm somewhat of an insomniac, so there is no standard 'lights out' time at night. I honestly don't notice them being affected much by the lights going on and off, and I don't see any difference in their general routine when I am at the cottage, where they get much more natural light. They tend to be active in the morning (hay o'clock!) and in the evening (play time, lap time, kids are at home and interacting more with them.) They doze a lot during the late morning/earlier afternoon, with occasional wandering around and eating/drinking. I do hear them drinking at night and occasionally squabbling over the pigloo at night, so it appears they are sporadically active even when it's quite dark, and I imagine they know their environment well and can smell their way around adequately to navigate even in the dark. Mine snooze most of the afternoon even though it's the brightest time for them, so I don't think a light would be affecting their sleep. They just don't have a long, sustained period of sleep like some other animals would. They are nappers by nature.
