oliverdavies.uk/modules/opd_presentations/src/Entity/Presentation.php

<?php

declare(strict_types=1);

namespace Drupal\opd_presentations\Entity;

use Drupal\Core\Datetime\DrupalDateTime;
use Drupal\node\Entity\Node;
use Drupal\node\NodeInterface;
use Drupal\opd_presentations\Collection\EventCollection;
use Drupal\opd_presentations\Entity\Event;

final class Presentation extends Node implements NodeInterface {

  public function getPastEvents(): EventCollection {
    $events = $this->get('field_events')->referencedEntities();

    $today = (new DrupalDateTime('today'))->format('U');

    return new EventCollection(array_filter(
      array: $events,
      callback: fn (Event $event): bool => $event->getEventDate() < $today,
    ));
  }

}