code: def formatday(self, day, weekday):
          
          if day and day in self.day_entries:
              day_date = date(self.current_year, self.current_month, day)
              archive_day_url = reverse('zinnia:entry_archive_day',
                                        args=[day_date.strftime('%Y'),
                                              day_date.strftime('%m'),
                                              day_date.strftime('%d')])
              return '<td class="%s entry"><a href="%s" '\
                     'class="archives">%d</a></td>' % (
                         self.cssclasses[weekday], archive_day_url, day)
  
          return super(Calendar, self).formatday(day, weekday)
docs: Return a day as a table cell with a link
          if entries are published this day.