test.php

<?php


$eventsRebuilded = array();
foreach($events as $event) {
  foreach($event->dates as $date) {
		$datestart = date('Y-m-d',strtotime($date->datestart));
		if(!isset($eventsRebuilded[$date->datestart])) {
			$eventsRebuilded[$date->datestart] = array();
		}
	}
}

foreach($eventsRebuilded as $dateKey => $value) {
	$time = strtotime($dateKey);
	foreach($events as $event) {
		foreach($event->dates as $date) {
			if($time >= strtotime($date->datestart) && $time <= strtotime($date->dateend)) {
				$eventsRebuilded[$dateKey][] = $event;
			}
		}
	}
}