If you want to change calender in propery view, then:
application\controllers\property.php, line around 720, before:
$this->load->library(‘calendar’, $prefs);
$this->load->library(‘calendar’, $prefs);
Add
$prefs['start_day'] = 'sunday';
Details about library configuration here:
https://ellislab.com/codeigniter/user-guide/libraries/calendar.html