calender()

Try moving these into your controller:

PHP Code:

<?php $this->load->helper('form'); ?> 
<?php $this->load->library('calendar');  ?>

Calling the loader from your view is likely to cause some issues in many circumstances, so it's best to avoid doing so. The documentation of the calendar library specifically states (emphasis mine):

Like most other classes in CodeIgniter, the Calendar class is initialized in your controller using the $this->load->library function

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide