Codeigniter Calendar - Populating

Hi I am wanting to use codeigniter to build a calendar however to populate the calendar you need to provide the day numbers how can i do this with a database design like so

id - int (10)

check_in - date

check_out - date

p.s it would need to fill in the dates to between

sample data

1,      2014-02-12      , 2014-02-15

2,      2014-02-15      , 2014-02-22

$this->load->library('calendar');

$data = array(
               3  => 'http://example.com/news/article/2006/03/',
               7  => 'http://example.com/news/article/2006/07/',
               13 => 'http://example.com/news/article/2006/13/',
               26 => 'http://example.com/news/article/2006/26/'
             );

echo $this->calendar->generate(2014, 6, $data);

http://ellislab.com/codeigniter%20/user-guide/libraries/calendar.html