code: private void processCalendarHours(ProjectCalendar calendar, Record dayRecord)
     {
        // ... for each day of the week
        Day day = Day.getInstance(Integer.parseInt(dayRecord.getField()));
        // Get hours
        List<Record> recHours = dayRecord.getChildren();
        if (recHours.size() == 0)
        {
           // No data -> not working
           calendar.setWorkingDay(day, false);
        }
        else
        {
           calendar.setWorkingDay(day, true);
           // Read hours
           ProjectCalendarHours hours = calendar.addCalendarHours(day);
           for (Record recWorkingHours : recHours)
           {
              addHours(hours, recWorkingHours);
           }
        }
     }
docs: Process hours in a working day.
  
  @param calendar project calendar
  @param dayRecord working day data