I spend a lot of my working day on conference calls with people from around the world. So much so that it’s a regular source of confusion when it’s the afternoon for me, but I’m wishing the Americans a good morning and the Indian guys in Bangalore a “good evening”.
Now “Good day” sounds too formal, and “hi” too informal, so I think we need a new phrase.
I propose “Good mornvenoon” as a timezone independent greeting.
Try it and see!