abdev

$installer = new Mage_Eav_Model_Entity_Setup('core_setup');
$entityTypeId = $installer->getEntityTypeId('catalog_product');

// replace <my_attribute_code> with your attribute code
$idAttribute = $installer->getAttribute($entityTypeId, '<my_attribute_code>', 'attribute_id');
$installer->updateAttribute($entityTypeId, $idAttribute, array(
   'backend_type' => 'varchar'
));
// let's see if it worked
$attribute = Mage::getModel('eav/entity_attribute')->loadByCode('catalog_product', '<my_attribute_code>');

abdev

$myDate = '07/10/12';//2012-07-10

$format = Mage::app()->getLocale()->getDateFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT);

$date = Mage::app()->getLocale()->date(
    $myDate,
    Mage::app()->getLocale()->getDateFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT),
    null, 
    false
);

abdev

   /**
     * {@inheritDoc}
     */
    public function getConfigTreeBuilder()
    {
        $treeBuilder = new TreeBuilder();
        $rootNode = $treeBuilder->root('my_root');

        $rootNode
            ->children()