title: Date.js parseExact() not parsing 4 digit years when passed in as an array
body: <p>Am I missing something with Date.parseExact() in date.js?  According to the api documentation, I should be able to do this:</p>
  
  <pre><code>Date.parseExact("10/15/2004", ["M/d/yyyy", "MMMM d, yyyy"]); // The Date of 15-Oct-2004
  </code></pre>
  
  <p>That is, I should be able to pass in a string array which contains "...the expected format {String} or an array of expected formats {Array} of the date string."  However, when I do this:</p>
  
  <pre><code>var d = Date.parseExact($(this).val(), ["MMddyy", "Mddyyyy", "MM/dd/yy","MM/dd/yyyy"])
  </code></pre>
  
  <p>I get back nulls for dates containing 4 digit years (that is, matching the MMddyyyy and MM/dd/yyyy formats).  Am I missing something or is this a bug in Date.js?</p>
  
  <p>Here is the complete block of code, for context:</p>
  
  <pre><code>$(function () {
       $('#FCSaleDate').change(function (e) {
           var d = Date.parseExact($(this).val(), ["MMddyy", "MMddyyyy", "MM/dd/yy","MM/dd/yyyy"])
           alert(d.toString("MM/dd/yyyy"));
       });
  
  });
  </code></pre>