code: private static synchronized BaseCalendar getJulianCalendarSystem() {
          if (jcal == null) {
              jcal = (JulianCalendar) CalendarSystem.forName("julian");
              jeras = jcal.getEras();
          }
          return jcal;
      }
docs: Returns the Julian calendar system instance (singleton). 'jcal'
  and 'jeras' are set upon the return.