code: public boolean isWorkingDay(Day day)
     {
        DayType value = getWorkingDay(day);
        boolean result;
  
        if (value == DayType.DEFAULT)
        {
           ProjectCalendar cal = getParent();
           if (cal != null)
           {
              result = cal.isWorkingDay(day);
           }
           else
           {
              result = (day != Day.SATURDAY && day != Day.SUNDAY);
           }
        }
        else
        {
           result = (value == DayType.WORKING);
        }
  
        return (result);
     }
docs: Method indicating whether a day is a working or non-working day.
  
  @param day required day
  @return true if this is a working day