<?php

defined( 'ABSPATH' ) or exit;

wp_clear_scheduled_hook( 'mc4wp_refresh_mailchimp_lists' );

$time_string = sprintf( 'tomorrow %d:%d%d am', rand( 1, 6 ), rand( 0, 5 ), rand( 0, 9 ) );
wp_schedule_event( strtotime( $time_string ), 'daily', 'mc4wp_refresh_mailchimp_lists' );
