auto remove past events from search engines (nofollow + sitemap) fror wpseo + tribe

past_events_wpseo_tribe.php

<?php
// gleaned from https://wordpress.org/support/topic/remove-past-events-from-xml-sitemap/#post-11431056

/* Modify the WP-SEO plugin's defaults */
if ( is_plugin_active( 'wordpress-seo/wp-seo.php' ) ) {

	/* add nofollow metatag to header of past events */
	add_filter("wpseo_robots", function($robots) {
	  if (! is_singular( 'exhibition' ) && tribe_is_past_event() == true) {
	    return "noindex,follow";
	  }
	  return $robots;
	});

   /* exclude past events from the sitemap */ 
	function my_find_expired_events( $ids ) {
		$args = array(
			'post_type'     => 'tribe_events',
			'nopaging'      => true,
			'fields'        => 'ids',
			'meta_query'    => array(
				array(
					'key'       => '_EventEndDate',
					'value'     => date( 'Y-m-d H:i:s' ),
					'compare'   => '<',
					'type'      => 'DATETIME',
				),
			),
		);
		$expired_events = get_posts( $args );
		$ids = array_merge( $ids, $expired_events );
		$ids = array_map( 'absint', $ids );
		$ids = array_unique( $ids );
		return $ids;
	}
	add_filter( 'wpseo_exclude_from_sitemap_by_post_ids', 'my_find_expired_events' );

}