class SixMonthlyAprilPeriodType extends SixMonthlyAbstractPeriodType {

    @Override
    public String getIsoDate( DateTimeUnit dateTimeUnit, Calendar calendar )
    {
        int month = dateTimeUnit.getMonth();

        if ( dateTimeUnit.isIso8601() )
        {
            month = calendar.fromIso( dateTimeUnit ).getMonth();
        }

        switch ( month )
        {
            case 4:
                return dateTimeUnit.getYear() + "AprilS1";
            case 10:
                return dateTimeUnit.getYear() + "AprilS2";
            default:
                throw new IllegalArgumentException( "Month not valid [4,10]" );
        }
    }

}