Change event date to TBD in Modern Event Calendar (aka MEC)

I want to change the date of a specific event to TBD, I can’t see any opton in Modern Event Calendar WordPress plugin. I have the php code but its not working.

add_filter('the_content', function($content) {
    if (is_singular('mec-events')) {
        $event_id = get_the_ID();
        $start_date = get_post_meta($event_id, 'mec_start_date', true);

        if ($start_date === '2099-12-31') {
            // Replace any date pattern with "TBD"
            $content = preg_replace('/d{1,2}s+w+s+d{4}/', 'TBD', $content);
            $content = str_replace('2099', 'TBD', $content); // fallback
        }
    }

    return $content;
});

I am adding this into code snippet but nothing changed.