Converting Data To Milliseconds

I would like some help to convert this function to the Cakephp standard. It takes the date from datetimepiker and it turns into milliseconds, but I searched a lot and did not find anything like that for CakePHP .

public function add()
{
    $this->db->set("start", $this->_formatDate($this->input->post("from")));
    $this->db->set("end", $this->_formatDate($this->input->post("to")));
}