I see that the format of the date element (in fact the group of <select>'s) can be managed by the format specified in the options array passed to the constructor, like this
PHP Code:
$form->addElement('date''date''Data', array('format'=>'dmY')); 
But the value returned by $form->exportValue('date') is an array whose keys are influenced by the display format.

Is there any way to get the date in a custom format (eg. "Y-m-d", for placing it in a query), independent of the display format?