title: How to check if a string is a legal "dd/mm/yyyy" date?
body: <p>Given a string <code>str</code>, how could I check if it is in the <code>dd/mm/yyyy</code> format and contains a legal date ?</p>
  
  <p>Some examples:</p>
  
  <pre><code>bla bla      // false
  14/09/2011   //         true
  09/14/2011   // false
  14/9/2011    // false
  1/09/2011    // false
  14/09/11     // false
  14.09.2011   // false
  14/00/2011   // false
  29/02/2011   // false
  14/09/9999   //         true
  </code></pre>