start = dtStart instanceof TimeValue
? new DateTimeValueImpl(start.year(), start.month(), 1, 0, 0, 0)
: new DateValueImpl(start.year(), start.month(), 1);
break;
case WEEKLY:
int d = (7 + wkst.ordinal() - Weekday.valueOf(dtStart).ordinal()) % 7;
start = TimeUtils.add(dtStart, new DateValueImpl(0, 0, -d));
break;
default: break;
}
}