Where date fields?

[dns2316]

created_at = models.DateTimeField(auto_now_add=True)

updated_at = models.DateTimeField(auto_now=True)

"auto_now, auto_now_add, and default are mutually exclusive
# options. The use of more than one of these options together
# will trigger an Error"

def pre_save(self, model_instance, add):
        if self.auto_now or (self.auto_now_add and add):
            value = timezone.now()
            setattr(model_instance, self.attname, value)
            return value
        else:
            return super(DateTimeField, self).pre_save(model_instance, add)

If field write auto, then not render this field in admin models?!