A day...

Does a day end? Is it that simple? When does a day really end? Is time linear? Or is time circular? Does time wrap around and never really end or does it stop and rebegin? Or does a day never end? If you look from the stars at the earth seeing all of creation the day never stops just continues around. If you are on earth the day ends when we sleep and begins a new when we awake. So a day really is what the eyes of a beholder see. There is more than one answer isn't there. Hmm...