如何在PHPExcel中将单元格值格式化为日期

我想在web中输出excel文件中的数据。excel中的一个单元格被格式化为日期，输出时返回如下：

A000001 |   John Doe      | DR | 41456 | 41465<--  // this should be date
A000002 |   Philip Moris  | CP | 41456 | 41465     // formatted as yyyy-mm-dd

require_once("controller/xls/Classes/PHPExcel/IOFactory.php");
$objPHPExcel = PHPExcel_IOFactory::load($filer);
foreach ($objPHPExcel->getWorksheetIterator() as $worksheet) 
{
    $worksheetTitle     = $worksheet->getTitle();
$highestRow         = $worksheet->getHighestRow(); // e.g. 10
$highestColumn      = $worksheet->getHighestColumn(); // e.g 'F'
$highestColumnIndex = PHPExcel_Cell::columnIndexFromString($highestColumn);
$nrColumns = ord($highestColumn) - 64;
echo '<table>';
for ($row = 5; $row <= $highestRow; ++ $row) 
{
echo '<tr>';
     for ($col = 1; $col < $highestColumnIndex; ++ $col)
     {
    $cell = $worksheet->getCellByColumnAndRow($col, $row);
    $val = $cell->getValue();
    echo '<td>'.$val.'</td>';
     }
echo '</tr>';
}
echo '</table>';
}

现在是unix时间吗？如果是，当我使用getCellByColumnAndRow时，我该如何格式化它？我还将把它存储在mysqldb中。Tnx。