include in library

[eluser]presto5[/eluser]
I have a library, where i'm trying to use the other class:

Code:

//.../datepicker.php
class datepicker {
  ...
}

Code:

//.../application/libraries/ig.php
<?php if (!defined('BASEPATH')) exit('No direct script access allowed');
include( base_url().'include/calendar/datepicker.php');

class Ig {
...
function some_function() {
$picker = new datepicker();
}
}

And when i'm trying to do:

Code:

$this->load->library('ig');
$this->ig->some_function();

it telling me:
Fatal error: Class 'datepicker' not found
Why???? I know for shure, that datepicker.php already included