Calendar c = (Calendar) calendar.clone();
        c.clear();
        c.set(Calendar.YEAR, this.year);
        c.set(Calendar.WEEK_OF_YEAR, this.week);
        c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek());
        c.set(Calendar.HOUR, 0);
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);
        c.set(Calendar.MILLISECOND, 0);