gistfile1.php

$result = $this->execute("SELECT * FROM wp_postmeta WHERE meta_key LIKE '_meta_box_id_application_date'");

if($result)
{
    foreach($result as $row)
    {
        $type = gettype($row['meta_value']);
        switch($type)
        case 'string':
            $date = date_from_string($row['meta_value']);
            $this->execute("UPDATE wp_postmeta SET meta_value = $row['meta_value'] WHERE meta_key = $row['meta_key']")
            break;
        case 'object': //assuming it's a date?
            //whatever you need to do, etc.
            break;
        
    }

}