Sunrise/Sunset are a visual cue that TV/movies use.
A sunrise is usually associated with a new beginning.
Sunset is a little different, as it can mean a variety of things depending on the context, it quite often means an ending of some sort.
i.e. in SW: AOTC at the very end we see cthe mass ranks of clone troopers and ships taking off with a sunset in the background added to the music cues it's bascially saying it's all downhill from here.
At the end of the Last crusade we see our herpos riding into the setting sun, which is a way of saying the end.