Advance Calendar day by x amounts
<p>Is there any difference between the following operations? (Advance current date to 160 days)</p>

<pre><code>    Calendar c = Calendar.getInstance();
    c.add(Calendar.DAY_OF_WEEK, 160);
    System.out.println(c);

    Calendar c0 = Calendar.getInstance();
    c0.add(Calendar.DAY_OF_MONTH, 160);
    System.out.println(c0);

    Calendar c1 = Calendar.getInstance();
    c1.add(Calendar.DAY_OF_YEAR, 160);
    System.out.println(c1);
</code></pre>

<p>I don't find any difference. So, which Calendar I should use instead?</p>
