public void test_minusDays_symmetry(LocalDateTime reference) {

    for (int days = 0; days < 365 * 8; days++) {
      LocalDateTime t = reference.minusDays(days).minusDays(-days);
      assertEquals(t, reference);

      t = reference.minusDays(-days).minusDays(days);
      assertEquals(t, reference);
    }
  }

  @Test(groups = { "tck" }