People refer to the various meals of the day as follows:
1. Breakfast, lunch, dinner.
2. Breakfast, dinner, supper.
What they are called probably relates to a person's social level in society, but not necessarily. Growing up on a farm, we farm folks had breakfast in the morning early, dinner around noon, and supper around 5-6 PM.
When my oldest brother married a city girl from an upper middleclass home, she and her family preferred breakfast, lunch, and dinner.
The more educated and refined people often say dinner instead of supper, although people from lower socioeconomic levels have gradually been going with breakfast, lunch, dinner, over time, maybe in an effort to at least pass for the higher social level, and not sound so much like a hick.
Even though my late husband was a graduate of Harvard Law School, I still like to call the last meal of the day supper. For one thing, it drives my daughter crazy, and isn't that what parents are for?
I'm not ashamed of having grown up in the country on a farm. I have plenty of education and most of my family has even more education than I do. I don't think growing up on a farm, or being of limited financial means is a characteristic of being poorly educated, or uneducated, or necessarily of low social status.
Even the Bible refers to the Last Supper, so how uncouth can the word supper really be? I think the word puts me in good company, if small company, referring to Jesus Christ and His disciples.
The reason you would walk a mile after supper (dinner) is so that you don't just go straight to bed and move all those calories straight to your backside. Walk a mile and get some exercise to work some of the calories, sugar, and fat off before they make themselves at home permanently. Always good to rest for about an hour after any meal and then get some exercise. Walk a mile, or jump rope for 15 minutes, or whatever you prefer to work some of those calories off.
The word supper has been a part of my vocabulary since before I could speak plainly enough to be understood (age 2 or so), and I have never heard of it referring to a meal after 12 AM. Who has meals then? Maybe somebody who works nights? Certainly not a majority of people. Maybe it is referred to as supper after 12 AM in some other country than the U.S. for some reason I know nothing about, but here in the states, it is as I stated.