That's how Greenwich time came to be the time from which all others are measured. But tell that to a working man or woman, whose day begins with an alarm clock going off. Or to a Jewish or Muslim religious whose new day begins at sundown of the previous day. A devout Muslim's day is divided by five calls to prayer. That's the source of much of the information in this report.
Birth begins the human clock.
Death ends it. The earth's sun was formed 4,500 million years ago. It has burned up less than half of its hydrogen fuel so far and has about 5,000 million years to go. Then it will end and with it any chance for life on earth. For many of the world's religions, the end will come when God or Jehovah or Allah calls the faithful to the Day of Judgment.