is it correct to use strtotime() to compare dates?
<p>I have some problems with the following:</p>

<pre><code>&lt;?php
echo "an issue by the function strtotime"."&lt;br /&gt;";
echo "01-30-2011 ======".strtotime(01-30-2011)."&lt;br /&gt;";
echo "01/30/2011 ======".strtotime(01/30/2011)."&lt;br /&gt;";
echo "07-01-2011 ======".strtotime(07-01-2011)."&lt;br /&gt;";
echo "07/01/2011 ======".strtotime(07/01/2011)
?&gt;
</code></pre>

<p>The result is
an issue by the function strtotime:</p>

<pre><code>01-30-2011 ======1310059868
01/30/2011 ======
07-01-2011 ======1310057768
07/01/2011 ======
</code></pre>

<ol>
<li>Which format is right to give argument to the function strtotime()?</li>
<li>Why is the epoch value changing during the page refresh, even though the argument isn't changed?</li>
</ol>
