Hola

Sensible people, the Spanish. When greeting each other we Brits routinely shorten good morning/afternoon/evening to morning/afternoon/evening.

Spaniards do it the other way round and truncate buenos dias/tardes/noches to buenos at all times of the day or night. It does make life that bit easier for visitors to their fine country and there's something delightfully optimistic about people meeting and simply saying "good", don't you think?