Mike's solution works like charm, as long as there are is no cell that contains two different formats. In that case the date in the date in the source cell is lost.

If one has merged cells, you might want to add this at the bottom in order to copy those as well:

            foreach (var regionSource in sourceWorksheet.MergedCellsRegions)
            {
                destination.MergedCellsRegions.Add(regionSource.FirstRow, regionSource.FirstColumn, regionSource.LastRow, regionSource.LastColumn);
            }

Same goes for shapes / images:

            foreach (WorksheetImage shapeSource in sourceWorksheet.Shapes)
            {
                WorksheetImage shapeDestination = new WorksheetImage(shapeSource.Image);
                shapeDestination.Outline = shapeSource.Outline;
                shapeDestination.TopLeftCornerCell = GetSameCellInOtherWorksheet(shapeSource.TopLeftCornerCell, destination);
                shapeDestination.TopLeftCornerPosition = shapeSource.TopLeftCornerPosition;
                shapeDestination.BottomRightCornerCell = GetSameCellInOtherWorksheet(shapeSource.BottomRightCornerCell, destination);
                shapeDestination.BottomRightCornerPosition = shapeSource.BottomRightCornerPosition;
                shapeDestination.PositioningMode = shapeSource.PositioningMode;
                destination.Shapes.Add(shapeDestination);
            }


        static WorksheetCell GetSameCellInOtherWorksheet(WorksheetCell sourceCell, Worksheet destinationWorksheet)
        {
            return destinationWorksheet.Rows[sourceCell.RowIndex].Cells[sourceCell.ColumnIndex];
        }

Hi - this code used to work in older versions, however in the latest version it yields the error:

Parameter name: value

at Infragistics.Documents.Excel.WorksheetCellFormatData.set_Style(WorkbookStyle value)
at Infragistics.Documents.Excel.WorksheetCellFormatData.SetFormatting(IWorksheetCellFormat source)

Is there a workaround for this? Unfortunately, I have come to rely heavily on this.