How to insert a date to an Open XML worksheet?

Question

I\'m using Microsoft Open XML SDK 2 and I\'m having a really hard time inserting a date into a cell. I can insert numbers without a problem by setting Cell.DataType = Cell

Answer 1

a) Get compatibility with Excel 2007, Excel 2007 Viewer etc. b) DateTime before 1.1.1900 write as string.

DateTime dat = (DateTime)dr[dc.ColumnName];

//Not working with Excel 2007
//cell.DataType = CellValues.Date;
//cell.CellValue = new CellValue(dat.ToString("s"));

double diff = (dat - new DateTime(1899, 12, 30)).TotalSeconds / 86400.0;
if (diff > 1)
{
    cell.DataType = CellValues.Number;
    cell.CellValue = new CellValue(diff.ToString().Replace(",", "."));

    if (dat.TimeOfDay == new TimeSpan(0))
    {                                
        cell.StyleIndex = 2;   //Custom Style NumberFormatId = 14 ( d/m/yyyy)
    }
    else
    {
        cell.StyleIndex = 1;   //Custom Style NumberFormatId = 22 (m/d/yyyy H:mm)
    }
}
else
{
    cell.DataType = CellValues.String;
    cell.CellValue = new CellValue(dat.ToString());
}