Inserindo Datapicker no system.xml do Magento

Block Include Datapicker

<?php
//salve as ModuleName/Block/Adminhtml/System/Config/Dataphicker.php
class Module_Name_Block_Adminhtml_System_Config_Datapicker extends Mage_Adminhtml_Block_System_Config_Form_Field
{
	protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
	{
		$date = new Varien_Data_Form_Element_Date;
		$format = Mage::app()->getLocale()->getDateFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT);

		$data = array(
			'name'      => $element->getName(),
			'html_id'   => $element->getId(),
			'image'     => $this->getSkinUrl('images/grid-cal.gif'),
		);
		$date->setData($data);
		$date->setValue($element->getValue(), $format);
		$date->setFormat(Mage::app()->getLocale()->getDateFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT));
		$date->setClass($element->getFieldConfig()->validate->asArray());
		$date->setForm($element->getForm());

		return $date->getElementHtml();
	}
}

Settings Datapicker

/.../
<quotation_validate>
    <label>Validade da cotação</label>
    <frontend_type>text</frontend_type>
    <frontend_model>modulename/adminhtml_system_config_datapicker</frontend_model>
    <sort_order>20</sort_order>
    <show_in_default>1</show_in_default>
    <show_in_website>1</show_in_website>
    <validate>required-entry</validate>
    <show_in_store>1</show_in_store>
</quotation_validate>
/.../