Demonstrate how to export excel and format datetime column(s) style for human readable.

ExcelExtenstion.cs

  public static class ExcelExtension {
      public static FileInfo Export<T> (string filepath, List<T> data) {
          ExcelPackage.LicenseContext = LicenseContext.NonCommercial;
          var output = new FileInfo (filepath);

          if (output.Exists) output.Delete ();
          if (!Directory.Exists (Path.GetDirectoryName (filepath))) Directory.CreateDirectory (Path.GetDirectoryName (filepath));

          using (var excel = new ExcelPackage (output)) {
              var ws = excel.Workbook.Worksheets.Add ("Sheet1"); // create sheet

              var rows = data.Count + 1; 

              if (rows > 0) {
                  ws.Cells[1, 1].LoadFromCollection (data, true, TableStyles.Medium16); // write data include header
              }

              var indexs = FindDateTimeColumns (data.FirstOrDefault ()).ToList ();
              indexs.ForEach (i => {
                  ws.Column (++i).Style.Numberformat.Format = "MM/dd/yyyy hh:mm:ss AM/PM"; // assign datetime style
              });

              ws.Cells.AutoFitColumns (); // fit the content width
              excel.Save (); // save all content
          }

          return output;

          // find out datatime column(s)'s correspond index, so we could force assign the style on its
          static IEnumerable<int> FindDateTimeColumns<T> (T obj) {
              var indexs = obj.GetType ()
                  .GetProperties ()
                  .Select ((item, index) => new { Item = item, Index = index })
                  .Where (o => o.Item.PropertyType == typeof (DateTime))
                  .Select (o => o.Index);

              return indexs;
          }
      }
  }