problem s java.util.Date

[danisevsky]

ahoj, mohl by mi prosim nekdo vysvetlit tuto metodu:

 public static void main(String[] args) throws ParseException {
        SimpleDateFormat format = new SimpleDateFormat("HH:mm:ss");
        Date date1 = format.parse("00:40:20");
        Date date2 = format.parse("00:30:10");
        Date date3 = new Date(date1.getTime() - date2.getTime());
        System.out.println(format.format(date3));
    }

vystup je: 01:10:10

proc to neni 00:10:10? kde se vzala ta hodina?
moc diky