old_contents: from datetime import date as vanilla_date, timedelta
  
  from .base import Calendar
  from ..constants import number_of_vanilla_dates
  from ..dates.bce import BCEDate
  from ..dates.distant import DistantDate
  
  
  class JulianDayNumber(Calendar):
      first_ce_day = vanilla_date(1, 1, 1)
      first_ce_day_number = 1721423
      display_name = "Julian Day Number"
      representation_keys = set(['day_number'])
  
      @staticmethod
      def date_display_string(d):
          n = JulianDayNumber._day_number(d)
          return "Day %d" % n
  
      @staticmethod
      def representation(d):
          return {'day_number': JulianDayNumber._day_number(d)}
  
      @staticmethod
      def _day_number(d):
          return (d - JulianDayNumber.first_ce_day).days + JulianDayNumber.first_ce_day_number
  
      @staticmethod
      def _bce_representation(n):
          count = 0 - n
          n_4_yr_periods = count // (365 * 4 + 1)
          remainder = count % (365 * 4 + 1)
          td = vanilla_date(8, 1, 1) - timedelta(days=remainder)
          year = td.year - 8 - 4 * n_4_yr_periods
          return (year, td.month, td.day)
  
      def date(self, n):
          offset = n - self.first_ce_day_number
          if offset >= 0 and offset <= number_of_vanilla_dates:
              vd = self.first_ce_day + timedelta(days=offset)
              return self.from_date(vd)
          elif offset > number_of_vanilla_dates:
              d = DistantDate(10000, 1, 1) + timedelta(days=offset)
          else:
              d = BCEDate(*self._bce_representation(offset))
              return self.from_date(d)
  
  class AstronomicalCalendar(Calendar):
      display_name = "Astronomical Calendar"
      representation_keys = set(['year', 'month', 'day'])
  
      @staticmethod
      def date_display_string(d):
          return "0/1/1"
  
      @staticmethod
      def representation(d):
          return dict(year=0, month=1, day=1)
  
      def date(self, y, m, d):
          try:
              vd = vanilla_date(y, m, d)
              return self.from_date(vd)
          except ValueError:
              d = None
              return self.from_date(d)
  
  
new_contents: from datetime import date as vanilla_date, timedelta
  
  from .base import Calendar
  from ..constants import number_of_vanilla_dates
  from ..dates.bce import BCEDate
  from ..dates.distant import DistantDate
  
  
  class JulianDayNumber(Calendar):
      first_ce_day = vanilla_date(1, 1, 1)
      first_ce_day_number = 1721423
      display_name = "Julian Day Number"
      representation_keys = set(['day_number'])
  
      @staticmethod
      def date_display_string(d):
          n = JulianDayNumber._day_number(d)
          return "Day %d" % n
  
      @staticmethod
      def representation(d):
          return {'day_number': JulianDayNumber._day_number(d)}
  
      @staticmethod
      def _day_number(d):
          return (d - JulianDayNumber.first_ce_day).days + JulianDayNumber.first_ce_day_number
  
      @staticmethod
      def _bce_representation(n):
          count = 0 - n
          n_4_yr_periods = count // (365 * 4 + 1)
          remainder = count % (365 * 4 + 1)
          td = vanilla_date(8, 1, 1) - timedelta(days=remainder)
          year = td.year - 8 - 4 * n_4_yr_periods
          return (year, td.month, td.day)
  
      def date(self, n):
          offset = n - self.first_ce_day_number
          if offset >= 0 and offset <= number_of_vanilla_dates:
              vd = self.first_ce_day + timedelta(days=offset)
              return self.from_date(vd)
          elif offset > number_of_vanilla_dates:
              d = DistantDate(10000, 1, 1) + timedelta(days=offset)
              return self.from_date(d)
          else:
              d = BCEDate(*self._bce_representation(offset))
              return self.from_date(d)
  
  class AstronomicalCalendar(Calendar):
      display_name = "Astronomical Calendar"
      representation_keys = set(['year', 'month', 'day'])
  
      @staticmethod
      def date_display_string(d):
          return "0/1/1"
  
      @staticmethod
      def representation(d):
          return dict(year=0, month=1, day=1)
  
      def date(self, y, m, d):
          try:
              vd = vanilla_date(y, m, d)
              return self.from_date(vd)
          except ValueError:
              d = None
              return self.from_date(d)
  
  
subject: Add missing return statement.