Writing Data to Excel for Date fileds

static void exportExcelFile(Args _args)
{
    SysExcelApplication     xlsApplication;
    SysExcelWorkBooks       xlsWorkBookCollection;
    SysExcelWorkBook        xlsWorkBook;
    SysExcelWorkSheets      xlsWorkSheetCollection;
    SysExcelWorkSheet       xlsWorkSheet;
    SysExcelWorksheetHelper worksheetHelper;
    SysExcelHelper          sysExcelHelper;
    VendRFQJour             vendRFQJour;
    VendTrans               vendTrans;
    int                     row = 1;
    str                     fileName;
    str                     worksheetName;
    Date                    deliveryDate;

    fileName    = "D:\\Sreekanth\\3553\\14062017\\Test.xlsx";

    //vendRFQJour = VendRFQJour::find("000103");
    vendTrans   = VendTrans::find(5637145355);

    worksheetName = strfmt("%1", date2str(systemdateget(),321,DateDay::Digits2,DateSeparator::None,DateMonth::Digits2,DateSeparator::None,DateYear::Digits4, DateFlags::None));
    sysExcelHelper = SysExcelHelper::construct();
    sysExcelHelper.initialize();
    xlsWorkSheet = sysExcelHelper.addWorksheet(worksheetName);

    worksheetHelper = SysExcelWorksheetHelper::construct(xlsWorkSheet);

    worksheetHelper.addColumn(1, 'RFQ Id', Types::String);
    worksheetHelper.addColumn(2, 'Delivery date', Types::Date);

    worksheetHelper.setCellValue(1, row, 'RFQId');
    worksheetHelper.setCellValue(2, row, 'DeliveryDate');
    row++;

    worksheetHelper.setCellValue(1, row, vendTrans.AccountNum);
    worksheetHelper.setCellValue(2, row, vendTrans.TransDate);

    if(WinApi::fileExists(fileName))
        WinApi::deleteFile(fileName);

    sysExcelHelper.save(filename);
    sysExcelHelper.close();

    info(strFmt("Creato file: %1", fileName));
}