Dinner was only ever the meal served in the middle of day when I went to school, hence school dinners, other than that I've always regarded it as an evening meal, except at Christmas, when dinner for us is the middle of the afternoon and we tend to refer to it as dinner not lunch.
Breakfast is generally the first meal of the day but I eat mine late anything between 11 am and 1 o'clock so it can morph into brunch.
Lunch is the middle of the day meal, if at home it usually consists of soup and a sandwich. If out in a restaurant it can be a full blown meal with wine and can go on till 4 pm, but in that case, for me it will then be the last meal of the day.
Tea is a middle of the afternoon type affair, my childhood memories of that would be with older relatives a delicious high tea affair complete with homemade scones and cake, the sort of thing we occasionally hanker after now and again and costs a considerable amount in some swanky establishment served with lashing of nostalgia and for a special treat a glass of Prosecco.
Supper is really posh talk for dinner, it was very well used when I lived in West London having received such invitations along the lines of "Do come to supper" never knowing whether to expect spag bol in the kitchen washed down with plonk or a formal dinner party affair in a dining room with place settings and all the cutlery for umpteen courses. that was all years ago though for the latter, I don't know anyone who can be bothered with all that palaver anymore, I know I can't , I prefer my entertaining to be informal lunches but they can, go on well into the evening, particularly if it's summertime and we are in the garden.