code: public static CalendarPeriod<CalendarQuarter> between(
          CalendarQuarter q1,
          CalendarQuarter q2
      ) {
  
          return new FixedCalendarPeriod<>(q1, q2, FixedCalendarTimeLine.forQuarters());
  
      }
docs: /*[deutsch]
  Erzeugt eine {@code CalendarPeriod} f&uuml;r die angegebene Quartalsspanne.
  
  @param   q1  first quarter year
  @param   q2  last quarter year (inclusive)
  @return  CalendarPeriod