Lunchtime,
Gritchka claims, is roughly between 13.00 and 14.00. While this may be the case in
London, the time when people eat
lunch have varied wildly in my experience.
Here in the States, I have found lunchtime to be an hour-long period beginning sometime no earlier than 11.00 and ending usually no later then 13.00. Here at my college, the cafeteria is open for lunch from 11.00 through 13.30, as people's class schedules vary. At my high school, it was 11.30-12.30. Back in elementary school, it was roughly 11.30-12.00.
Everything in France, except, of course, for restaurants, absolutely shuts down from 12.00 to 14.00 (or occasionally 13.00-15.00) so that every Frenchman can enjoy his proper, leisurely 2-hour lunch.
In Spain, lunch is generally eaten much later, roughly sometime between 13.30 and 16.00, though it usually only lasts 45-90 minutes. Many Spaniards leave work around 13.30 or 14.00, return home for lunch and sometimes a siesta (it's not a myth), then return to work around 16.00-17.00 to work for another three hours. Lunch is the main meal of the day, and is often referred to in Spain simply as comida—"food".
When I was in southern Mexico, I found that lunch was often consumed before siesta, starting around 12.00-13.00.