code: public void setCalendar(ProjectCalendar calendar)
     {
        set(TaskField.CALENDAR, calendar);
        setCalendarUniqueID(calendar == null ? null : calendar.getUniqueID());
     }
docs: Sets the name of the base calendar associated with this task.
  Note that this attribute appears in MPP9 and MSPDI files.
  
  @param calendar calendar instance