private RegularTimePeriod createInstance(Class periodClass, 
                                             Date millisecond, TimeZone zone) {
        RegularTimePeriod result = null;
        try {
            Constructor c = periodClass.getDeclaredConstructor(new Class[] {
                    Date.class, TimeZone.class});
            result = (RegularTimePeriod) c.newInstance(new Object[] {
                    millisecond, zone});   
        }
        catch (Exception e) {
            // do nothing            
        }
        return result;