title: regex - date format OR not specified/empty
body: <p>I have a regex problem that I need some advice on.  I am using a jquery plugin that validates input fields on a JSP.  I am using the date validation.  It all works fine but this field is not required and is not marked as required.  When the user hits submit it shows a warning on the date input field since the empty string does not match the validation of a date.  I need some way to say that nothing or a date is valid in a regex.</p>
  
  <p>Here is the regex for the date; is there any way to put "or empty" into this also:</p>
  
  <pre><code>"date":{
             "regex":"/^[0-9]{1,2}\-\[0-9]{1,2}\-\[0-9]{4}$/",
             "alertText":"* Invalid date, must be in MM-DD-YYYY format"},
  </code></pre>
  
  <p>Thanks in advance</p>