So it's finally clear...dinner is a more "low class" name for an evening meal. Supper is used in "upper classes"( "dinner" is a term reserved for a formal evening meal). An average evening family meal is supper. If you are having a formal evening "out" at a restaurant then it can be called dinner.
Also where I come from, the Canadian prairies, dinner often refers to the noon meal because this is when most farm families have a large meal. The farmers working out on the field need some hearty nourishment at noon, often they have been working on their fields since sunrise. By evening they are exhausted and just look for a light meal(supper) and early bedtime! I find that people in Ontario and the U.S. refer to dinner as the evening meal. Strange, I could never call supper, dinner.