auto expiring WordPress posts by custom timestamp (unix)

auto_expire_posts.php

define( 'EV_POST_TYPE', 'event' );
define( 'EV_DATE_FIELD', 'event_start_date' );
define( 'EV_TIMESTAMP', 'event_timestamp' );

// save start date as unix timestamp
function custom_timestamp ( $post_id ) {

	$ev_post_type 		= 'event';
	$ev_date_field		= 'event_start_date';
	$ev_timestamp 		= 'event_timestamp';
	
	if ( get_post_type( $post_id ) == $ev_post_type ) :
		
		$the_date = get_post_meta($post_id, $ev_date_field, true);
		if( $the_date ) :
			$timestamp = strtotime( $the_date );
			update_post_meta( $post_id, $ev_timestamp, $timestamp  );

		endif;
	endif;
}
add_action( 'save_post', 'custom_timestamp', 100, 2);



// SCHEDULE DAILY OLD EVENT REMOVAL RUN ----------------------- 

function remove_expired_events() {
	if ( ! wp_next_scheduled( 'delete_expired_events' ) ) :
		wp_schedule_event( time(), 'twicedaily', 'delete_expired_events');
	endif;
}
add_action( 'wp', 'delete_expired_events' );

// REMOVE EVENTS OLDER THAN TODAY -----------------------------
function delete_expired_events() {
	
	$today = time() + 86400; // add one day to keep from deleting today's events
	$args = array(
		'post_type' => $ev_post_type,
		'posts_per_page' => -1,
		'meta_query' => array(
	 		array(
	    	'key'     => $ev_timestamp,
				'value'   => $today,
				'compare' => '<',
	  	)
		)
	);
	
	$expired = new WP_Query( $args );

	//  Cycle through each Post ID
	if ( $expired->have_posts() ) :
		while ( $expired->have_posts() ) :
			$expired->the_post();
			wp_delete_post( get_the_ID() );
		endwhile;
	endif;
	wp_reset_postdata();
}

add_action( 'remove_expired_events', 'expired_event_delete' );