将此添加到functions.php 活动（子）主题的文件-

add_action( \'init\', \'wpse_393267_activate_plugin\' );
function wpse_393267_activate_plugin() {

    if( !function_exists( \'is_plugin_active\' ) ) {
        include_once ABSPATH . \'/wp-admin/includes/plugin.php\';
    }

    $plugin_to_activate = \'jetpack/jetpack.php\'; // plugin-dir/plugin-file.php
    $date_to_activate   = \'2021-08-13\'; // YYYY-MM-DD

    if( is_plugin_active( $plugin_to_activate ) ) return;

    if( time() >= strtotime( $date_to_activate ) ) {
        activate_plugin( $plugin_to_activate );
    }
}