code: def get_start_balance(self, before: date) -> Decimal:
          
          assert isinstance(before, datetime)
  
          # create a new date without hours
          datum = Datum()
          datum.from_date(before)
          #date_corrected = datetimeutils.start_of_day(before)
          # now subtract 1 second.
          #date_corrected -= timedelta(seconds=1)
          #log(DEBUG, "getting balance on %s", date_corrected)
          datum.yesterday()
          datum.end_of_day()
          return self.get_balance_on(datum.value)
docs: Calculates account balance