PeriodValue period = IcalParseUtil.parsePeriodValue(dateStr);
DTBuilder b = new DTBuilder(period.start());
StringBuilder out = new StringBuilder();
while (true) {
DateValue d = b.toDate();
if (d.compareTo(period.end()) > 0) { break; }
if (0 != out.length()) { out.append(','); }
out.append(d);
b.day += interval;
}
return out.toString();