It's a simple question in my mind, but I am at a blank at the moment...

Basically, I am wondering how it would be possible to determine the length of the day and night on a theoretical moon (especially as the cycle should be pretty thrown off by reflected light from the planet it would orbit). Mostly because there's so much talk about life being possible on moons rather than on gas giants, that it leads me to wondering if life, even if the moon was located in the habitable zone, would ever be able to survive the moon's temperature and light changes.

Although I initially decided that the theoretical moon had to have 50-50 sunlight and complete darkness through its 'year' (orbiting the planet once), I realised I hadn't taken into account a potential retrograde orbit; or any light that might be bent off a potential atmosphere on the plant. Or, for that matter, an orbit that isn't at the same angle of its planet.

In short, is there a formular for day/night cycles similar to that of orbits

T^2 = C x A^3

where T would be orbital time, C would be a constant and A would be average distance from whatever the object is orbiting?

So far, my attempts of finding any solutions other than scaled models and lightbulbs, have only ended with Librarians hissing when I go near them, and Google happily offering me telescopes and zodiac readings in its ads...

Or am I just making stuff unneededly complex, and the answer is really 50% constant night and 50% constant sunny day for the whole moon?