code: public static CalendarWeek from(GregorianDate date) {
  
          PlainDate iso = PlainDate.from(date); // includes validation
          return CalendarWeek.of(iso.getInt(PlainDate.YEAR_OF_WEEKDATE), iso.getInt(Weekmodel.ISO.weekOfYear()));
  
      }
docs: /*[deutsch]
  <p>Konvertiert das angegebene gregorianische Datum zu einer Kalenderwoche. </p>
  
  @param   date    gregorian calendar date (for example {@code PlainDate}
  @return  CalendarWeek
  @throws  IllegalArgumentException if given date is invalid
  @since   3.28/4.24