Hi Mike,

Please find a sample exemple code which try to explain you which kind of problem i found.This problem occur only for 2007 Excel format, never for Excel 2003 format. Also it occur only if you export in an existing excel file.

DataTable data = new DataTable();

// data is filled from a database. First column is DateTime format


// first time , excel file and worksheetName doesn't exist
workBook = new Workbook();
worksheet = workBook.Worksheets.Add(worksheetName);

foreach (DataRow datarow in data.Rows)
{
    for (int columnIndex = 0; columnIndex < datarow.ItemArray.Length; columnIndex++)
    {
        row.Cells[columnIndex].Value = datarow[columnIndex];
    }               
}

// Save xlsx excel file
// ---------------------
// Export DateTime column is ok, it  has the right format like dd/mm/yyyy (French culture)
// ---------------------
workBook.Save(xlsxFile);


// Second time excel file and worksheetName exist
workBook = Workbook.Load(xlsFile);

// Remove the worksheetName
workBook.Worksheets.Remove(workBook.Worksheets[worksheetName]);

worksheet = workBook.Worksheets.Add(worksheetName);

foreach (DataRow datarow in data.Rows)
{
    for (int columnIndex = 0; columnIndex < datarow.ItemArray.Length; columnIndex++)
    {
        row.Cells[columnIndex].Value = datarow[columnIndex];
    }               
}

// Save xlsx excel file
// ---------------------
// Now, export DateTime column is ok but it  has a wrong  format like 39976
// ---------------------
workBook.Save(xlsxFile);

Hi Florent,

I'm not sure I understand exactly what you are describing. Can you post a small sample project and give me some steps I can follow in order to duplicate the problem?