In my books I used them for scene changes. So in my example above, that would be two different chapters. I also try not to let chapters get far out of time sync, but you can only tell one thing at a time so there can be some time shifting.
However if the events are not connect (like in the example) the exact timing on them might not matter at all, so if the reader assumes the second chapter happens after the first it will not impact the story. If the timing is important I might start the chapter with "Mean while..." or some other clear indication of time.
If a chapter is less then say 700 words, I start questioning whether or not the scene should be there at all. I have a few places where I let a short chapter go, but for very specific reason. I just was wondering if I was being reasonable or not
