well my five cents worth, as Spanish ,who have travelled the country. the meal times gets extended as you go south ,generally speaking. Nowdays with the advent of modernity and corporate schedules, even in the south meals are been serve more flexible. And it will continue to change although slowly ::)

You can eat anytime you want, anything, But ,the general times for meals are pretty much as is
breakfast 8:30 to 10 am
Lunch 2-4 pm
dinner 10-12midnite, i know but i have often eaten by 11:30 pm

the in between you can have "snacks", tapas, drinks, horchatas, etc anytime.