Events Manager 5.8.x does not create $this->event_id so event doesn't really exist.

em-create-event-basic.php

<?php

define('WP_USE_THEMES', false);

/** Loads the WordPress Environment and Template */
require( dirname( __FILE__ ) . '/wp-blog-header.php' );


$event_name = 'EM Test';
$event_start_date = '2017-12-02';
$event_time = '12:13:14';
$event_description = '<p>This is the description of EM Test event.</p>';

$location_id = 1;

// STOP EDITING.

$event_end_date = $event_start_date;
$event_start_time = $event_time;
$event_end_time = $event_start_time;
                        
$EM_Event = new EM_Event();
$EM_Event->event_name = $event_name;
$EM_Event->post_content = $event_description;
//$EM_Event->event_owner = $author_id;
$EM_Event->location_id = $location_id;

$EM_Event->event_start_date = $event_start_date;
$EM_Event->event_end_date = $event_end_date;
$EM_Event->event_start_time = $event_start_time;
$EM_Event->event_end_time = $event_end_time;
// Convert start and end date/time to a Unix timestamp.
$EM_Event->start = strtotime($EM_Event->event_start_date.' '.$EM_Event->event_start_time);
$EM_Event->end = strtotime($EM_Event->event_end_date.' '.$EM_Event->event_end_time);

$EM_Event->save();
                        
echo '<p>Event post ID: ', $EM_Event->post_id, '</p>';
echo '<p>Event event ID: ', $EM_Event->event_id, '</p>';


global $EM_Notices;
echo $EM_Notices::__toString();