Javascript sort not working in Firefox
<p>I have the following code which is sorting a list of javascript objects in an array based on their date. The data is coming from an XML file. The date is formatted as follows: MM-DD-YYYY</p>

<pre><code>concert=new Object();
concert.performer=performerName;
concert.date=concertDate;
concerts[0]=concert; //adding to array in a for loop
</code></pre>

<p>So at this stage I have a load of concert objects in my concerts array.
I then go to sort it and output it to a table:</p>

<pre><code>sortedConcerts = concerts.sort(sortConcerts);

function sortConcerts(a, b){
var firstConcert=new Date(a.date);
var secondConcert=new Date(b.date);
return firstConcert-secondConcert;
}
</code></pre>

<p>I then have the new sorted array which I print out using a table or whatever.</p>

<p>My problem is that this works fine in IE and Chrome, but not in Firefox... what does Firefox not like?</p>
