def METHOD_NAME(self, date_range):
    with pytest.raises(ValidationError):
        n = 365
        times = date_range("2000-01-01", freq="12H", periods=n)
        da = xr.DataArray(
            np.arange(n), [("time", times[::-1])], attrs=self.tas_attrs
        )
        tg_mean(da)