POI 创建日期格式单元格

Workbook wb = new HSSFWorkbook();xxx.xls 文件可用此操作
    //Workbook wb = new XSSFWorkbook();xxx.xlsx 文件需要用到 xssfworkbook
    CreationHelper createHelper = wb.getCreationHelper();
    Sheet sheet = wb.createSheet("new sheet");建立一个名为 new sheet 的表单

    // Create a row and put some cells in it. Rows are 0 based.
    Row row = sheet.createRow(0);

    // Create a cell and put a date value in it.  The first cell is not styled
    // as a date.
    Cell cell = row.createCell(0);
    cell.setCellValue(new Date());

    // we style the second cell as a date (and time).  It is important to
    // create a new cell style from the workbook otherwise you can end up
    // modifying the built in style and effecting not only this cell but other cells.
    CellStyle cellStyle = wb.createCellStyle();
    cellStyle.setDataFormat(
        createHelper.createDataFormat().getFormat("m/d/yy h:mm"));
    cell = row.createCell(1);
    cell.setCellValue(new Date());
    cell.setCellStyle(cellStyle);

    //you can also set date as java.util.Calendar
    cell = row.createCell(2);
    cell.setCellValue(Calendar.getInstance());
    cell.setCellStyle(cellStyle);

    // Write the output to a file
    FileOutputStream fileOut = new FileOutputStream("workbook.xls");
    wb.write(fileOut);
    fileOut.close();