'Test the diff in both directions, validate they are the same and of opposite signs.'

def test_sign(self):

    d1 = datetime.datetime(2000, 1, 1, 0, 0, 0, 0)
    d2 = datetime.datetime(2000, 1, 1, 0, 0, 0, 1)
    self.assertTrue((datediff(d1, d2) < 0), 'First    date    earlier    than    the    second    returns    negative.')
    self.assertTrue((datediff(d2, d1) > 0), 'Second    date    earlier    than    the    first    returns    positive.')
    self.assertTrue((datediff(d2, d2) == 0), 'First    date    equals    the    second    returns    0.')
