code: def get_day_start_ut_span(self):
          
          cur = self.conn.cursor()
          first_day_start_ut, last_day_start_ut = \
              cur.execute("SELECT min(day_start_ut), max(day_start_ut) FROM days;").fetchone()
          return first_day_start_ut, last_day_start_ut
docs: Return the first and last day_start_ut
  
          Returns
          -------
          first_day_start_ut: int
          last_day_start_ut: int