code: public static Date addWeeks(Date date, int iWeeks) {
      Calendar dateTime = dateToCalendar(date);
      dateTime.add(Calendar.WEEK_OF_YEAR, iWeeks);
      return dateTime.getTime();
    }
docs: Adds the specified (signed) amount of weeks to the given date. For
  example, to subtract 5 weeks from the current date, you can
  achieve it by calling: <code>addWeeks(Date, -5)</code>.
  
  @param date   The time.
  @param iWeeks The amount of weeks to add.
  
  @return A new date with the weeks added.