It seems like a simple enough concept, but even after 3+ months here, I just can't seem to get the hang of the buenos dias/buenas tardes/buenas noches greetings. Clearly, for the locals, it's completely instinctive to know which of the three to use at any particular moment. But for me, when I go to greet someome, I always have to stop and think o.k., it's 4:28 p.m., that's the afternoon, right? before I can blurt out: "Buenas tardes!"
I have been thinking about changing my sleeping patterns. My new daily routine could be simplify the problem somewhat, for by getting up at noontime, I would have been able to eliminate the need for buenos dias and reduce my greeting possibilities to just two.
Last Thursday, for example, I had to get up early and meet up with a whole bunch of people at about 6:30 a.m. Since the sun was up, I greeted them all with buenas tardes! I bet they thought I was drunk.