code: public ProjectCalendar getDefaultCalendar()
     {
        String calendarName = m_properties.getDefaultCalendarName();
        ProjectCalendar calendar = getCalendarByName(calendarName);
        if (calendar == null)
        {
           if (m_calendars.isEmpty())
           {
              calendar = addDefaultBaseCalendar();
           }
           else
           {
              calendar = m_calendars.get(0);
           }
        }
        return calendar;
     }
docs: Retrieves the default calendar for this project based on the calendar name
  given in the project properties. If a calendar of this name cannot be found, then
  the first calendar listed for the project will be returned. If the
  project contains no calendars, then a default calendar is added.
  
  @return default projectCalendar instance