Warning: date() expects parameter 2 to be long

I am receiving this error below. This error appears when viewing the Sermon listing on the dashboard and does not display the sermons on the front end.

Warning: date() expects parameter 2 to be long, string given in /wp-content/plugins/sermon-manager-for-wordpress/includes/template-tags.php on line 178

The code in question is:

function wpfc_sermon_date_filter() {
	global $post;
	if ( 'wpfc_sermon' == get_post_type() ) {
		$ugly_date = get_post_meta($post->ID, 'sermon_date', 'true');
		$date = date(get_option('date_format'), $ugly_date);
			return $date;
	}
}
//add_filter('get_the_date', 'wpfc_sermon_date_filter');

Any ideas?

https://www.ads-software.com/plugins/sermon-manager-for-wordpress/