So, a colleague of mine, who's in a place with 10 hr time difference than mine, called me up during my morning (9am), his late night (11pm), and said "Good Morning". As this happened for the first time with me, I just replied with "Oh hello. Good ... err Night ... to you" & had a few seconds of awkward moment & continued with our work talk.
So I was wondering, what would be my proper response in this situation?