public void test_difference_days() {
    Date d1 = Dates.newDate(2010, 1, 1, 12, 30, 0);
    Date d2 = Dates.newDate(2010, 1, 1, 10, 0, 0);
    assertEquals(0, Dates.differenceDays(d1, d2));

    Date d3 = Dates.newDate(2010, 1, 10, 10, 0, 0);
    assertEquals(8, Dates.differenceDays(d3, d1));
  }