              value = value.isoformat()
              if value.endswith('+00:00'):
                  value = value[:-6] + 'Z'
              return value
          return value.strftime(self.format)
  
  
  class DateField(Field):
      default_error_messages = {
          'invalid': _('Date has wrong format. Use one of these formats instead: {format}.'),
 
</s> remove         return value.strftime(self.format)
 </s> add         return value.strftime(output_format) </s> remove         return value.strftime(self.format)
 </s> add         return value.strftime(output_format) </s> remove     format = api_settings.TIME_FORMAT
    input_formats = api_settings.TIME_INPUT_FORMATS
 </s> add  </s> remove     format = api_settings.DATE_FORMAT
    input_formats = api_settings.DATE_INPUT_FORMATS
 </s> add  </s> remove         if self.format.lower() == ISO_8601:
 </s> add         if output_format.lower() == ISO_8601:
        return value.strftime(output_format)
              value = value.isoformat()
              if value.endswith('+00:00'):
                  value = value[:-6] + 'Z'
              return value
        return value.strftime(output_format)
  
  
  class DateField(Field):
      default_error_messages = {
          'invalid': _('Date has wrong format. Use one of these formats instead: {format}.'),
keep keep keep keep replace keep keep keep keep keep
 Access settings lazily, not at module import 
rest_framework/fields.py