I know it's been done to death but the issue has reared its ugly head again on another thread.
I am a Northerner who went to school in the south ( in case that affects anything).
Dinner is not eaten at a specific time of day. It is the largest/most formal/main meal of the day but can be eaten at any time.
All the other meal names are time dependent:
Breakfast (first meal of the day when you break your overnight fast)
Morning coffee/elevenses (obvious)
Luncheon ( always eaten in the middle of the day)
Tea ( at teatime: may be an afternoon tea and or a high tea)
Supper (last meal of the day eaten mid-late evening.
Not all meals are compulsory and some may be blended (eg Brunch) .
When lunch is the main meal of the day it may be described as dinner (school dinner, Sunday dinner, Christmas dinner). When tea and supper are combined into a main meal then a large evening meal may be described as dinner.
It may not be necessary to call any meal dinner if you choose to label meals based on time of day.
So I think that the divide between those who call their evening meal dinner or tea is less to do with geography and more to do with whether or not their parents had an early evening meal followed by a later snack supper or if they had a big meal and nothing later.
Does that make sense to anyone but me? DH says that I'm overthinking 😀 and that no one cares, but I've been on MN long enough to know that someone cares (apart from me).