使用Divi将更新日期添加到WordPress帖子时出现问题..？

I am working with WordPress / Divi. I would like to add the Updated Date to my posts.

I found this tutorial about how to do this, which offers this code that I have applied:

/**
 * Adds Updated on date/time to every blog post.
 *
 */
function et_last_modified_date_blog( $the_date ) {
    if ( 'post' === get_post_type() ) {
        $the_time = get_post_time( 'His' );
        $the_modified = get_post_modified_time( 'His' );

        $last_modified =  sprintf( __( 'Last updated %s', 'Divi' ), esc_html( get_post_modified_time( 'M j, Y' ) ) );
        $published =  sprintf( __( 'Published on %s', 'Divi' ), esc_html( get_post_time( 'M j, Y' ) ) );

        $date = $the_modified !== $the_time ? $last_modified . ' | ' .  $published : $published;
        echo 'Date Value: ' . $date;
        exit();
        return $date;
    }
}
add_action( 'get_the_date', 'et_last_modified_date_blog' );
add_action( 'get_the_time', 'et_last_modified_date_blog' );

This does display as expected on the front-end post content:

However, it results in the following on the back-end admin panel under the Activity section:

Warning: date() expects parameter 2 to be integer, string given in /home/username/sandbox_woocommerce/wp-admin/includes/dashboard.php on line 868

It seems that the function is changing date from an actual date that PHP/WordPress wants to a general string that's getting output on the post content. This doesn't seem proper to me, but I'm struggling to figure out the best way to resolve it.

Any information on how I can adjust this to get what I'm wanting without breaking things elsewhere would be greatly appreciated. Thanks!