🎃 Switches the active theme using the ThemeSwitcher Pro register method, based on a specific date. In this case, Halloween in the US (October 31st)

tsp_is_halloween_example.php

<?php
/*
Plugin Name: Halloween Theme Switch Code
Description: Switches the theme to a special Halloween theme only on October 31st.
Author: Brad Williams
Version: 1.0
Author URI: https://webdevstudios.com
*/

/**
 * Checks if the current PHP date is October 31.
 *
 * @return boolean true if the current day is October 31, otherwise false.
 */
function isHalloween() {
    $today = new DateTime();
    return $today->format('m') == '10' && $today->format('d') == '31';
}

function tsp_custom_date_switching() {
	if ( ! class_exists( 'TSP_Manager' ) ) {
		return;
	}

	/**
	 * The theme slug of the theme you want to use on Halloween.
	 */
	$theme_slug = 'twentytwentyfive';

	/** 
     * Registers a custom theme switching condition, 
     * using the TSP_Manager::register method. 
     */
    TSP_Manager::register(
	    $theme_slug,
	    function () {
		    return isHalloween();
	    },
	    1
    );
}
add_action( 'plugins_loaded', 'tsp_custom_date_switching', 100 );