"Christmas lunch is what most of our readers would eat, not Christmas dinner. Use the latter only if referring specifically to an evening meal."
http://www.telegraph.co.uk/topics/about-us/style-book/143530...
https://books.google.com/ngrams/graph?content=Christmas+lunc...
Also this:
https://trends.google.co.uk/trends/explore?q=Christmas%20lun...
In spanish you have 3 distinct meals, 'desayuno' 'almuerzo' and 'cena' mapping strictly to a moment of the day, more or less 'breakfast' 'lunch' and 'dinner', with the option of a merienda (roughly 'tea' but usually just sweet food like cookies or some such) between lunch and dinner. Each of this happens on a specific moment of the day (morning, noon, the optional afternoon thing and well into nighttime).
Are there other languages/dialects where the word maps the importance of the meal instead of the actual time it is consumed?
One other great British-English question is "what do you call an individually portioned baked bread article" ... roll, barm, bap, cob, ...
I was always told that dinner (from "dine") is the main meal of the day. So if you have a 'fancy' afternoon meal that can be your dinner (e.g. we usually do Christmas dinner between 3 and 4).
I wonder if HN knows of a linguistic map for meal names, it appears that these words shift meaning a lot.
EDIT: I thought this was interesting -- "Harvard's Dialect Survey had the question, 'What is the distinction between dinner and supper?' Here's the geographic distribution of their results from 10,661 American respondents" https://english.stackexchange.com/questions/22446/lunch-vs-d...