if (onset.getMonth() == 0) return null;
if (!onset.hasRule()) return null;
    private static String toICalRRule(SimpleOnset onset) {        if (onset.getMonth() == 0) return null;        StringBuffer sb =            new StringBuffer("FREQ=YEARLY;WKST=MO;INTERVAL=1;BYMONTH=");        sb.append(onset.getMonth()).append(";BYDAY=");        sb.append(onset.getWeek()).append(sDayOfWeekNames[onset.getDayOfWeek()]);        return sb.toString();    }