How do I set cell value to Date and apply default Excel date format?

Question

I\'ve been using Apache POI for some time to read existing Excel 2003 files programmatically. Now I have a new requirement to create entire .xls files in-memory (still using

Answer 1

To know the format string used by Excel without having to guess it: create an excel file, write a date in cell A1 and format it as you want. Then run the following lines:

FileInputStream fileIn = new FileInputStream("test.xlsx");
Workbook workbook = WorkbookFactory.create(fileIn);
CellStyle cellStyle = workbook.getSheetAt(0).getRow(0).getCell(0).getCellStyle();
String styleString = cellStyle.getDataFormatString();
System.out.println(styleString);

Then copy-paste the resulting string, remove the backslashes (for example d/m/yy\ h\.mm;@ becomes d/m/yy h.mm;@) and use it in the http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells code:

CellStyle cellStyle = wb.createCellStyle();
CreationHelper createHelper = wb.getCreationHelper();
cellStyle.setDataFormat(createHelper.createDataFormat().getFormat("d/m/yy h.mm;@"));
cell = row.createCell(1);
cell.setCellValue(new Date());
cell.setCellStyle(cellStyle);