Negative DateInterval
<p>I want to create a DatePeriod object with a negative DateInterval.</p>

<p>This creates a DatePeriod with the year increasing from today to 2016.</p>

<pre><code>$this-&gt;Set('dates', new DatePeriod(new DateTime(), new DateInterval('P1Y'), new DateTime('2016-06-06')));
</code></pre>

<p>I want to start at 2016, and using a negative DateInterval move towards todays year</p>

<p>Something like this might illustrate my desire</p>

<pre><code>$this-&gt;Set('dates', new DatePeriod(new DateTime('2016-06-06'), new DateInterval('-P1Y'), new DateTime()));
</code></pre>

<p>I just can't find any extended info on either DatePeriod or DateInterval on how to do this. All i find is that DateInterval can be inverted.</p>
