If moths are attracted to light why do they sleep during day time?

Firstly, the attraction towards light is called phototactic. Moths exhibit a specific character as what we call as a "positive phototactic". The reason why they do not come out during the day is due to highly sensitive body. Sun rays can lead to their demise. At night, they use the sky/stars as a method to navigate/migrate. Moths prefer low illumination scenario, where they can easily catch signals and then move at night. During the day, this will not be possible due to the extra large amount of supply of light. Not proven theories about Moths getting blinded with extra ordinary supply of light could be sited as another reason.

Moths use the moon to navigate and mistake lights at night as the moon.  So they will either spiral in or spiral away from the moon while trying to fly in a straight line.  This is mistakenly interpreted as 'moths being attracted to light' (many different insects similarly navigate by the moon at night).

Moths are nocturnal (active period :night), and most nocturnal creatures select this life style to avoid predators and to reduce competition. Avoid predators Moths avoid many day time predators include reptiles,birds and mammals by choosing a nocturnal life style. Lepidopterans (include moths,butterflies) main predators are birds, moths avoided bird predation by switching to nocturnal life and by avoiding the active time of birds. But Owls, bats, several mammals choose nocturnal life and they feast on moths. Reduce competition Moths reduce competitions for food(rotting organic matter) by switching to nocturnal life and there by avoiding other lepidopterans who feeds on the same food.Attraction to light is a property of moth, they rely on Cosmic light sources for flight orientations, their most reliable friend is the Moon, although certain moths rely on Sonar for travelling and it is said that some moths can even jam the sonar of bats and there by overcome predation.It isn't matter that you need to be always in the broad day light for being photo-axial, moths have a sensory attraction for light sources, they tend to navigate with the help of light. But their circadian rhythm allows them to be active during the night and inactive(sleep ?) in day time.

In addition to nocturnal moths, there are a large number of day flying moths and moths that are active during the day and at night. The hummingbird hawk moth is a great example of a powerful day flying moth and moths such as the "Silver Y" moth are active during the day and the night.