It was my understanding that these two spells cancel each other out. If darkness is cast on a "lit" are, the light goes out. Conversely, if light is cast in a "dark" area, the dark goes out. (

What is the absence of dark?

)
Is this the case? Are the spells supposed to cancel one another? If they are supposed to, they do not. If they are not supposed to, then how does it work?