Dinner is the main and most formal meal in your day. It can be at noon or in the evening. Whatever meal is not dinner goes by lunch at noon or supper in the evening.
Sunday dinner is usually after church around noon. Thanksgiving dinner is around noon, as well. If you were to eat again later in the day, it would be your supper.
You may remember I collect vintage etiquette books. According to Emily Post...
“Whether a meal is correctly called dinner or supper depends upon what is served. At dinner, soup is always served in plates (with rims) and eaten with a tablespoon. Coffee is always black and servee-d in demitasse (or half cups) cups after dinner. At supper, soup is served in cups or bowls. Coffee is served with cream in breakfast cups during the meal. There is also a difference in the menu, such as a roast with dinner, and minced or hashed or other made-over meat, or else cold meat for supper.”
Breakfast is much less complicated.