How to create form with date element, to insert user input to the database table?

Hi
I have problem with form which I have created after reading the form API and all the other stuff about forms. I am trying to create one sample form to save user input into a database table. For the sake of understanding the process of form development I have tried to use textfield, date, select, radios and submit button. To insert this data into the database table I am using db_query. Most of the data is going to the database table except the “date”. I have tried many options to resolve this problem but unable to solve it. Following is the table structure;

CREATE TABLE `emp` (
`emp_id` int(10) unsigned NOT NULL auto_increment,
`name` varchar(45) NOT NULL default '',
`designation` varchar(45) NOT NULL default '',
`dob` date NOT NULL default '0000-00-00',
`division` varchar(45) NOT NULL default '',
`gender` tinyint(1) NOT NULL default '0',
PRIMARY KEY (`emp_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='test table';

Following is the test module for creating form;

 //Code Starts here-----------
<?php
// $Id$
/**
* Implementation of hook_menu().
*/
function testform_menu($may_cache) {
$items = array();
if ($may_cache) {
$items[] = array(
'path' => 'testform',
'title' => t('The Test Form'),
'callback' => 'testform_page',
'access' => TRUE
);
}
return $items;
}
/**
* Called when user goes to example.com/?q=testform
*/
function testform_page() {
$output = t('This page contains our Employee Data Entry Form.');
// Return the HTML generated from the $form data structure.
$output .= drupal_get_form('testform_nameform');
return $output;
}

/**
* Defines a form.
*/
function testform_nameform() {

$form['emp_details']['name'] = array(
'#title' => t('Name'),
'#type' => 'textfield',
'#description' => t('Please enter your name.'),
'#required' => TRUE
);

//EMP designation
$form['emp_details']['designation'] = array(
'#title' => t('Designation'),
'#type' => 'textfield',
'#description' => t('Please enter your designation.'),
'#required' => TRUE
);

//EMP dob
$form['emp_details']['dob'] = array(
'#title' => t('Date of Birth'),
'#type' => 'date',
'#description' => t('Please enter your date of birth.'),
'#required' => TRUE,
'#default_value' => array(
'year' => format_date(time(), 'custom', 'Y'),
'month' => format_date(time(), 'custom', 'n'),
'day' => format_date(time(), 'custom', 'j')
)
);

//EMP division
$form['emp_details']['division'] = array(
'#title' => t('Division'),
'#type' => 'select',
'#required' => TRUE,
'#options' => array(t('div-1'), t('div-2'), t('div-3')),
'#description' => t('Please select your division.'),
);

//EMP gender
$form['emp_details']['gender'] = array(
'#title' => t('Gender'),
'#type' => 'radios',
'#required' => TRUE,
'#description' => t('Please select your gender.'),
'#options' => array(
t('Male'),
t('Female')
),
);

//Submit Button
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Save')
);
return $form;
}
/**
* Handle post-validation form submission.
*/
function testform_nameform_submit($form_id, $form_values) {
  db_query("INSERT INTO {emp} (name, designation, dob, division, gender) VALUES ('%s', '%s', %d, '%s', '%s')", $form_values['name'], $form_values['designation'], $form_values['dob'], $form_values['division'], $form_values['gender']);
  drupal_set_message(t('Your form has been saved.'));
}
//Code ends here -----------
?>

Please help me in understanding and creating forms in Drupal.
Thanks in advance…