code: private void readCalendars(Project ganttProject)
     {
        m_mpxjCalendar = m_projectFile.addCalendar();
        m_mpxjCalendar.setName(ProjectCalendar.DEFAULT_BASE_CALENDAR_NAME);
  
        Calendars gpCalendar = ganttProject.getCalendars();
        setWorkingDays(m_mpxjCalendar, gpCalendar);
        setExceptions(m_mpxjCalendar, gpCalendar);
        m_eventManager.fireCalendarReadEvent(m_mpxjCalendar);
     }
docs: This method extracts calendar data from a GanttProject file.
  
  @param ganttProject Root node of the GanttProject file