code: public static CalendarPeriod<CalendarWeek> between(
          CalendarWeek w1,
          CalendarWeek w2
      ) {
  
          return new FixedCalendarPeriod<>(w1, w2, FixedCalendarTimeLine.forWeeks());
  
      }
docs: /*[deutsch]
  Erzeugt eine {@code CalendarPeriod} f&uuml;r die angegebene Wochenspanne.
  
  @param   w1  first calendar week
  @param   w2  last calendar week (inclusive)
  @return  CalendarPeriod