public static DateTime offsetMonth(Date date, int offset) {
		return offset(date, DateField.MONTH, offset);
	}
@Test
	public void offsetMonthTest() {
		final DateTime st = DateUtil.parseDate("2018-05-31");
		final List<DateTime> list = new ArrayList<>();
		for (int i = 0; i < 4; i++) {
			list.add(DateUtil.offsetMonth(st, i));
		}
		assertEquals("2018-05-31 00:00:00", list.get(0).toString());
		assertEquals("2018-06-30 00:00:00", list.get(1).toString());
		assertEquals("2018-07-31 00:00:00", list.get(2).toString());
		assertEquals("2018-08-31 00:00:00", list.get(3).toString());
	}