gistfile1.php

<?php

/**
 * Customize Event Query using Post Meta
 * 
 * @author Bill Erickson
 * @link http://www.billerickson.net/customize-the-wordpress-query/
 * @param object $query data
 *
 */
function be_event_query( $query ) {
	
	if( $query->is_main_query() && !$query->is_feed() && !is_admin() && $query->is_post_type_archive( 'event' ) ) {
		$meta_query = array(
			array(
				'key' => 'be_events_manager_end_date',
				'value' => time(),
				'compare' => '>'
			)
		);
		$query->set( 'meta_query', $meta_query );
		$query->set( 'orderby', 'meta_value_num' );
		$query->set( 'meta_key', 'be_events_manager_start_date' );
		$query->set( 'order', 'ASC' );
		$query->set( 'posts_per_page', '4' );
	}

}

add_action( 'pre_get_posts', 'be_event_query' );