Answer:
There are several different greeting for different times of the day and situations.
ohaiyo gozaimasu - "good morning" until about noon.
konnichiwa - "good afternoon" until 5 pm or so.
konbanwa - "good evening" the rest of the day.
moshi moshi - "hello" on the telephone.
o genki desu ka - "how are you"
yokoso - "welcome" (to a place)