Dinner is the largest meal by default, whether at mid day or evening. Here is an explanation of both followed by my experiences in daily life (in the USA) and Europe.
Breakfast dinner supper was/is used by people with a ‘rural’ lifestyle. You get up at sunrise (6 o’clock) work for about 6 hours, eat a big meal around noon (dinner) work till the evening (6 o’clock) eat a small meal (supper) and got to sleep in an hour or two.
Breakfast lunch dinner is used by people with 8 to 5 jobs: get up around 7 eat a small meal, got to work. By 1–2 take a half hour break and eat a medium meal (lunch) and get home at about 6–7 after running errands and eat a dinner.
I personal eat breakfast lunch dinner and supper but my breakfast and supper are very very small (less than 300c) i eat at 6:30 breakfast, 12:00 lunch 4:00 dinner 8:00 supper
when i visit family in Poland (Europe) they use a 7:00 breakfast, 1:00 dinner and 6:00 supper.