Filter event list query for The Events Calendar plugin to show events that start 30 days from now

filter_event_list_query_args.php

<?php
add_filter( 'tribe_events_list_widget_query_args', 'jm_filter_list_widget_query_args' );
/**
 * Filter the query used for the Event List Widget to show only events starting
 * in the future
 */
function jm_filter_list_widget_query_args( $args ) {

	$offset = 86400 * 30;
	$date = date( 'U' ) + $offset;

	$args['eventDisplay'] = 'list';
	$args['meta_query'] = array(
		array(
			'key'     => '_EventStartDate',
			'value'   => date( 'Y-m-d H:i:s', $date ),
			'compare' => '>=',
			'type'    => 'DATETIME',
		),
	);

	return $args;

}