def get_url(self):
        """
        The URL at which the detail page should appear.

        By default it is /archive/ + the year in self.year_format + the
        month in self.month_format + the day in the self.day_format.
        An example would be /archive/2016/01/01/.
        """
        return os.path.join(
            '/archive',
            self.get_year(),
            self.get_month(),
            self.get_day()
        )