Quick Greetings

おはようございます
Ohayou gozaimasu - Good Morning. This is normally said until about 10:00am

こんにちは
Konnichiwa - Good Afternoon / Hello

こんばんは
Konbanwa - Good Evening

お やすみなさい
Oyasuminasai - Good Night. This is normally said when going to bed to sleep

さようなら
Sayounara - Goodbye