timestamp

[eluser]mehwish[/eluser]
hi please tell me how do i insert values in database field with type timestamp. Like i am doing this way in codeigniter

Code:

$user_poll_query=array(
                                'description'=>$poll_query,
                                     'creator_id'=>$user_id,
             'valid_from'=>date('Y-m-d H:i:s','1299762201428'),
                               );
         $this->db->insert('sl_polls',$user_poll_query);

but in databse i am getting 0s (0000-00-00 00.00.00)