code: def _calc_daystamps(self, st_time, end_time):
          
          start_doy = sum(self._num_of_days_each_month[:st_time.month-1]) + st_time.day
          end_doy = sum(self._num_of_days_each_month[:end_time.month-1]) + end_time.day + 1
          return list(range(start_doy, end_doy))
docs: Calculate days of the year between start time and end time.
  
          Use this method only when start time month is before end time month.