index.php

<?php
/**
 * Plugin Name:       Custom Code Snippets - Display Eventbrite
 * Version:           1.0
 */
add_filter( 'wfea_cal_extra_options',
    function ( $options ) {
       $options['fullcalendar']['showNonCurrentDates'] = false;

       return $options;
    },
10,
1
);