Formatting Dates in JExcel

Jexcel has an annoying Feature: It exports Dates always as UTC.
They have published some kind of workaround for reading Excelfiles, but it does not work for Writing Excel files.
My workaround:

TimeZone tz = TimeZone.getDefault();
int offset = tz.getOffset(date.getTime());
Calendar cal = new GregorianCalendar();
cal.add(Calendar.MILLISECOND, offset);
DateTime datetime = new DateTime(j,i, cal.getTime());
WritableCellFormat cf = new WritableCellFormat(df);