s1.add(new Task("Task 2", new Date(10L), new Date(11L)));
        assertFalse(d1.equals(d2));
        TaskSeriesCollection u2
                = (TaskSeriesCollection) d2.getUnderlyingDataset();
        TaskSeries s2 = u2.getSeries("Series");
        s2.add(new Task("Task 2", new Date(10L), new Date(11L)));
        assertTrue(d1.equals(d2));