Allow the admin to bypass any scheduling restrictions to make a booking in the backend.

admin-no-schedule-restrictions-for-rtb.php

<?php
/**
 * Plugin Name: Allow Admin Override of Scheduling Restrictions for Restaurant Reservations
 * Plugin URI: http://themeofthecrop.com
 * Description: Allow the admin to create a booking at any time.
 * Version: 0.0.1
 * Author: Theme of the Crop
 * Author URI: http://themeofthecrop.com
 * License:     GNU General Public License v2.0 or later
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU
 * General Public License as published by the Free Software Foundation; either version 2 of the License,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write
 * to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */
defined( 'ABSPATH' ) || exit;

add_filter( 'rtb-setting-schedule-open', 'aaosrrtb_modify_schedule_open' );
function aaosrrtb_modify_schedule_open( $schedule_open ) {

	if ( !is_admin() ) {
		return $schedule_open;
	}

	return array(
		array(
			'weekdays' => array(
				'monday' => 1,
				'tuesday' => 1,
				'wednesday' => 1,
				'thursday' => 1,
				'friday' => 1,
				'saturday' => 1,
				'sunday' => 1,
			)
		)
	);
}

add_filter( 'rtb-setting-schedule-closed', 'aaosrrtb_modify_schedule_closed' );
function aaosrrtb_modify_schedule_closed( $schedule_closed ) {

	if ( !is_admin() ) {
		return $schedule_closed;
	}

	return array();
}