public void testSetToFirstDayOfMonth() {
    // Start in middle of month
    {
      Date date = new Date(99, 5, 15);
      CalendarUtil.setToFirstDayOfMonth(date);
      assertTrue(CalendarUtil.isSameDate(new Date(99, 5, 1), date));
    }

    // Start on first day of month
    {
      Date date = new Date(99, 5, 1);
      CalendarUtil.setToFirstDayOfMonth(date);
      assertTrue(CalendarUtil.isSameDate(new Date(99, 5, 1), date));
    }
  }