@Lilliwyt I say good morning whenever I get up regardless of the time, and good night when I go to sleep regardless of the time. I often go to bed at like noon, and get up like 6pm. So...yeah, I think it's just a nice gesture to say whenever you wake up or sleep regardless of the hour, and a bit funny, the idea to me applies more to the cycle of waking up and sleeping rather than the hour/day & night cycle.