Help with cronjob command line

Ok, after much messing and testing, I have got it to work but there is just something wrong with 4 lines.

in the controller its

PHP Code:

$timestamp = strtotime("+1 days");
$appointments = $this->Appointment_model->get_days_appointments($timestamp); 


in the model

PHP Code:

$this->db->where('start_time < ', $day_start);
$this->db->where('start_time > ', $day_end); 


If I take out the where in the model it all works perfectly (for a test), I add this to just get the next day appointments and nothing happens as it cannot find any (even though there is one on every day for the next 6 days).

Can anyone see what I am missing with it as the time system has always been my weak point.

Just incase, here is the day_start and day_end incase its theses too.

PHP Code:

$day_start = date('Y-m-d 00:00:00', $day);
$day_end = date('Y-m-d 23:59:59', $day);