About Dinner and lunch and supper in US
Dinner is the main meal of the day. In the not to distant past, it was usually served mid-day.
Supper or lunch was an other meal. (Breakfast, of course was the first meal of the day)

Now days, most urban dwellers, in US at any rate, eat there dinner in the evening, at supper time. For many, dinner and supper have become synonyms.

Country folk in US, still often have there dinner as the midday meal. But even when they change there eating habits, the language lags, and the still often refer to their midday meal as dinner.