code: public ProjectCalendarHours addCalendarHours(Day day)
     {
        ProjectCalendarHours bch = new ProjectCalendarHours(this);
        bch.setDay(day);
        m_hours[day.getValue() - 1] = bch;
        return (bch);
     }
docs: Used to add working hours to the calendar. Note that the MPX file
  definition allows a maximum of 7 calendar hours records to be added to
  a single calendar.
  
  @param day day number
  @return new ProjectCalendarHours instance