code: public void addDateHeader (@Nonnull @Nonempty final String sName, @Nonnull final LocalDateTime aLDT)
    {
      addDateHeader (sName, PDTFactory.createZonedDateTime (aLDT));
    }
docs: Add the passed header as a date header.
  
  @param sName
  Header name. May neither be <code>null</code> nor empty.
  @param aLDT
  The LocalDateTime to set as a date. May not be <code>null</code>.