def _calculate_solar_time_by_doy(self, hour, doy):
        """This is how radiance calculates solar time.

        This is a place holder and \
        need to be validated against calculateSolarTime.
        """
        raise NotImplementedError()
        return (0.170 * math.sin((4 * math.pi / 373) * (doy - 80)) -
                0.129 * math.sin((2 * math.pi / 355) * (doy - 8)) +
                12 * (-(15 * self.time_zone) - self.longitude) / math.pi)