Well for mi its like this
9:30 tea break or second breakfast
11ish pm supper
Think it all depends what your social standing is, or your social aspirations are on what you call each meal. I hve noticed theres no debate about what breakfast is called
I think it used to be like that down here when I was a kid. We looked forward to school dinner at midday as the big feed of the day. Then I think 'Taking Lunch' crept in amongst the managerial classes and filtered down. In all the factories I worked in, dinner break was midday. When they got closed dinner seemed to go with them. Places I worked after that started to have 'Lunch breaks' of a half-hour instead of 'Dinner break' of an hour. As the old folk died off the idea of 'dinner' for the midday meal gradually faded out. Dinner in the early evening became the main meal of the day.
Now we're mostly retired we have 'Afternoon tea' at about 4 o'clock, but this is a bit of a joke on our part, and probably amuses the neighbours, because if one of us is out in the garden the other rings a handbell to tell them afternoon tea is served....