return lessonStart.plusDays(getLessonWeekDay() - lessonStartDayOfWeek);
return lessonStart.plusDays(getLessonWeekDayToYearMonthDayFormat() - lessonStartDayOfWeek);
    private YearMonthDay getLessonStartDay() {        YearMonthDay periodStart = getRoomOccupation().getPeriod().getStartYearMonthDay();        int weekOfQuinzenalStart = (getWeekOfQuinzenalStart() != null) ? getWeekOfQuinzenalStart().intValue() : 0;        YearMonthDay lessonStart = periodStart.plusDays(7 * weekOfQuinzenalStart);              int lessonStartDayOfWeek = lessonStart.toDateTimeAtMidnight().getDayOfWeek();        return lessonStart.plusDays(getLessonWeekDay() - lessonStartDayOfWeek);    }