I am sure this has been debated before !
I have lunch, if I have it all, at between 12:00 and 13:30. Sometimes I might have "Brunch" a little earlier. especially if I have missed breakfast.
Tea would a meal with with very small sandwiches and cakes, at about 15:00'ish.
Nursery Tea, if served at all, is a little later, and might include poached eggs on toast.
Dinner is rather late in my house, and is always eaten at about 20:00, and is the main meal of the day. Wine is almost always served, and there should be some kind of pudding as well, preferably with custard.