function setDate($year = null, $month = null, $day = null)
{
if (!isset($year)) {
$year = parent::format('Y');
}
if (!isset($month)) {
$month = parent::format('m');
}
if (!isset($day)) {
$day = parent::format('d');
}
if ($day < 0) {
$day += RepeatRuleDateTime::daysInMonth($year, $month) + 1;
}
parent::setDate($year, $month, $day);
return $this;
}
