First should declare two variables in model
public $from_date,$to_date;
Then add following lines in the search function [model]
if(!empty($this->to_date) && !empty($this->from_date))
{
$criteria->condition = "dat  between '$this->from_date' and  '$this->to_date'";
}
The following lines need in the view file to display form
<div id="search">
$this->beginWidget('zii.widgets.CPortlet', array(
'title'=>"Search",
));
<?php 
$form=$this->beginWidget('CActiveForm', array( 'id'=>'page-form',                                                                   	                                                            	'enableAjaxValidation'=>true,)); 
?>
																			
	<b>From :</b>
	<?php
$this->widget('zii.widgets.jui.CJuiDatePicker', array(
       'name'=>'from_date',  // name of post parameter
					'value'=> '',//Yii::app()->request->cookies['from_date']->value,
		     'options'=>array(
					  	'showAnim'=>'fold',
						       'dateFormat'=>'yy-mm-dd',
					),'htmlOptions'=>array(
				       'style'=>'height:20px;'
				       ),
				       ));
     ?>
<br /><b>To :</b>
  	<?php
     $this->widget('zii.widgets.jui.CJuiDatePicker', array(
		'name'=>'to_date',
				     'value'=> '',//Yii::app()->request->cookies['to_date']->value,
					'options'=>array(
								     'showAnim'=>'fold',
								  	'dateFormat'=>'yy-mm-dd',
								  	),
				     'htmlOptions'=>array('style'=>'height:20px;),));
       ?>
  <?php echo CHtml::submitButton('Search',array('id'=>'searchbtn')); ?>
     [b]<?php $this->endWidget(); ?>[/b]
<?php $this->endWidget();?>
                         	
</div>
Finally add following lines in the controller/admin function
if(!empty($_POST))
{
$model->from_date = $_POST['from_date'];
$model->to_date = $_POST['to_date'];
}
Thats it!