convert excel date to javascript date
                                function ExcelDateToJSDate(serial) {
   var utc_days  = Math.floor(serial - 25569);
   var utc_value = utc_days * 86400;                                        
   var date_info = new Date(utc_value * 1000);
   var fractional_day = serial - Math.floor(serial) + 0.0000001;
   var total_seconds = Math.floor(86400 * fractional_day);
   var seconds = total_seconds % 60;
   total_seconds -= seconds;
   var hours = Math.floor(total_seconds / (60 * 60));
   var minutes = Math.floor(total_seconds / 60) % 60;
   return new Date(date_info.getFullYear(), date_info.getMonth(), date_info.getDate(), hours, minutes, seconds);
}