you can use the m-d-Y format for dates. the format must be Y-m-d
change:
$_POST['date2'] = "".((isset($_POST["date2"]))?date("d-m-y", strtotime($_POST["date2"])):"") ."";
to:
$_POST['date2'] = "".((isset($_POST["date2"]))?date("Y-m-d", strtotime($_POST["date2"])):"") ."";