In the United States, there is great confusion over the proper naming of meals. Few people really know the answer to the question, “Is it called supper, or dinner?” Traditionally, in England, where so many of our customs in the U.S. come from, Dinner is the meal consumed in the middle of the day, and is the most sumptuous and involved. Supper, also referred to as Tea, is the last meal of the day, consumed in the evening, and consists of very light fare, such as crumpets, biscuits, teas, and milk-based drinks, perhaps with a bit of cereal.
Dinner is also used to describe the evening meal when it refers to a formal social meal, with dress codes and strict protocols. The menu is usually quite sophisticated. This is where the phrase “to dine” comes from. It means to attend a lavish, feast-type meal, usually with non-family members and guests present, in a formal setting.
The word supper comes from the French word souper, and was descriptive of the French custom of having a light meal of soup, bread, cheese and wine in the evening. It is still used to describe this meal in French-Canadian, French Belgian, and French-Swiss cultures.
Whether 'supper', or 'dinner' is used in modern times is sometimes a function of class distinction., or to differentiate between a working-class evening meal with the family, or a sumptuous feast for distinguished guests. Supper is used for an informal family meal served in the kitchen, or family dining room, and dinner is used to describe a formal meal with guests, a dress code, protocols, your best china, etc....
The biblical 'Last”, or 'Lord's' Supper was called that (although not in the scriptures themselves) because it was the last meal of the day, and consisted of very light and simple fare, such as bread, wine and maybe a little cheese. This was the basis for the start of Holy Communion, or the Eucarist, which is a bread-based wafer, and a sip of wine, or juice, symbolic of Jesus's last meal.
Dinner usually involves more preparation, and more involved dishes being served, such as soufflés, steaks, and other fine-dinning fare. This is why intimate outings with a member of the opposite sex, with possible romantic aspirations, are referred to as 'Dinner-Dates'. The object is to impress your date with your knowledge of culinary arts, and good taste, rather than nourishment. By contrast, married couples, good friends, and family members go out for supper, usually burgers, hot dogs, or other fun foods, where the object is just fellowship, and satisfying hunger.
So, traditionally, it is the object of the event that defines the terms, rather than the time of day. A good way to keep them straight is “Dinner for impressing, supper for digesting.”
If you think you know the answer to the question, “ Is it called supper, or dinner?”, you may still be jumping the gun. As usual, in the United States, we have once again managed to muddy up the waters, and confuse a normally easy-to-understand social custom. The U.S. mentality is based on the concept of Free-Enterprise, which means we seldom interfere with anything business does, unless it is absolutely necessary. This is why workers in America work more, and longer hours than any other free industrialized nation. During our accepted work day, which can be as long as 14 hours, or more, most businesses allow employees the bare minimum time to eat possible, and only so that the workers won't collapse from hunger while on the job. Most workers get 30 minutes to eat, which includes travel time to and from the place where they will eat, ordering and serving time, and waiting time. This usually works out to around maybe 10 minutes to wolf-down something simple, as fast as you can, maybe even in your car on the way back to work. This time constraint rules out most fresh, or complicated food, and most fare is either sandwiches, prepared way ahead of time, food off of a “Roach-Coach”, which is a mobile restaurant with questionable sanitation, and health characteristics, or super-fast foods at places like McDonald, Burger King, etc... We call this meal lunch, because many times, it's what you will be losing later...and no other terms fit. Workers usually go home in the evening, and finally get to enjoy a large sit-down meal with the family, after which they usually conk out in front of the TV set, until their other-half ('spouse', in America...) wakes them up to come to bed. This is probably the main reason why Americans are losing the Battle of the Bulge (obesity...). Any doctor will tell you that eating a lot of food, then going to sleep for 6 or more hours is a great way to put on unwanted weight. Ideally, you should eat light at night, and eat a large breakfast, or a big noon meal, so you have the rest of the day to work off the calories. True to form, we here in the United States insist on doing things backwards to the rest of the world.
Whether you call the evening meal dinner, or supper depends on the desired outcome of the event. So, use your own judgment when telling people about what you had to eat last night. Let them wonder 'Is it called supper, or dinner?' Does it really matter that much, as long as you get to eat?