def METHOD_NAME(self):
    self.assertFalse(units.Units('days').isreftime)
    self.assertFalse(units.Units('years').isreftime)
    self.assertFalse(units.Units('kg').isreftime)
    for u in self.get_test_reftimes():
        with self.subTest(test_u=u):
            self.assertTrue(u.isreftime)
    for u in self.get_test_reftimes(calendar='julian'):
        with self.subTest(test_u=u):
            self.assertTrue(u.isreftime)
    for u in self.get_test_reftimes(time= '12:34:56', calendar='noleap'):
        with self.subTest(test_u=u):
            self.assertTrue(u.isreftime)
    for u in self.get_test_reftimes(unit='minutes', time= '12:34:56',
        calendar='proleptic_gregorian'):
        with self.subTest(test_u=u):
            self.assertTrue(u.isreftime)