/**
 * @param  <String>	Wochentag	Analog date('D')
 * @param  <Integer>	Monat
 * @param  <Integer>	Jahr
 * @return <DatePeriod>
*/
function findWeekdays($weekday, $month, $year) {
	$dateFrom = clone $dateTo = DateTime::createFromFormat('d.n.Y', "1.{$month}.{$year}");   
	$dateFrom->modify('first day of  +0 month');
	$dateTo->modify('last day of  +0 month');
	$interval = DateInterval::createFromDateString("next {$weekday}");
	return new DatePeriod($dateFrom, $interval, $dateTo, DatePeriod::EXCLUDE_START_DATE);
}