มีวิธีแปลงค่า serial number ใน excel เป็น date ด้วย php ไหมคะ

<?php
/** PHPExcel */
require_once 'PHPExcel/Classes/PHPExcel.php';

/** PHPExcel_IOFactory - Reader */
include 'PHPExcel/Classes/PHPExcel/IOFactory.php';


$inputFileName = "uploads/date.xlsx";  
$inputFileType = PHPExcel_IOFactory::identify($inputFileName);  
$objReader = PHPExcel_IOFactory::createReader($inputFileType);  
$objReader->setReadDataOnly(true);  
$objPHPExcel = $objReader->load($inputFileName);  


$objWorksheet = $objPHPExcel->setActiveSheetIndex(0);
$highestRow = $objWorksheet->getHighestRow();
$highestColumn = $objWorksheet->getHighestColumn();

$headingsArray = $objWorksheet->rangeToArray('A1:'.$highestColumn.'1',null, true, true, true);
$headingsArray = $headingsArray[1];

echo '<pre>';
echo "headingsArray<br>";
var_dump($headingsArray);
echo '</pre><hr />';

include("app.php");  //** connect database **//


$namedDataArray = array();
for ($row = 2; $row <= $highestRow; ++$row) {
    $dataRow = $objWorksheet->rangeToArray('A'.$row.':'.$highestColumn.$row,null, true, true, true);
    if ((isset($dataRow[$row]['A'])) && ($dataRow[$row]['A'] > '')) {
        
        foreach($headingsArray as $columnKey => $columnHeading) {
            $namedDataArray[$r][$columnHeading] = $dataRow[$row][$columnKey];
        }

		foreach($dataRow[$row] as $col => $value){

				echo $value."<br>";

		}

    }
}



?>