One thing I've noticed is that Japanese people will say "Good morning" to you if it's the morning where THEY are, rather than where you are.
So if I phoned someone in the US and it was morning over there but lunchtime here in the UK, I'd say "Good morning" whereas a Japanese person would say "Konnichiwa"..
Has anyone else noticed this or is it something I've just made up?! If it is true I guess it's because there's a difference in meaning between "Good morning" and "Ohayou gozaimasu" even though they're used in the same way.