Passing GET value show error

hi , sorry for english :

 i make a script to simulate a agenda , passing a data to a controller agenda/visualizza_settimana/day_of_week as (Y:m:d) show the week . Now i want search a data by a field type date , select a data and in my controller have 

$this->load->view('agenda/visualizza_settimana/'.$uk_date)

 but have this error : Unable to load the requested file: agenda/visualizza_settimana/2017-09-13.php , if i insert 2017-09-13 as parameter manually it work properly , why ?

Work properly if i use redirect instead $this->load->view too.