Append the date to main navigation menu via functions.php

functions.php

<?php
// I need to make sure that scripts and styles are able to be recognized on the website.
        function HC_Scripts() {
                wp_enqueue_style('style'  , get_stylesheet_uri());
        	wp_enqueue_style('grid'   , get_template_directory_uri() .'/grid.css', array(), null, 'all');
                wp_enqueue_style('fonts'  , 'https://fonts.googleapis.com/css?family=PT+Sans:400,400i|Roboto+Condensed:400,700', false );
                wp_enqueue_style('load-fa', 'https://maxcdn.bootstrapcdn.com/font-awesome/4.6.3/css/font-awesome.min.css' );
        }
        add_action( 'wp_enqueue_scripts', 'HC_Scripts' );
?><?php
// Here I'm making sure that menus are sorted out and flexible
        register_nav_menus(array(
            'primary' => __('Primary Header Menu'),
            'footer'  => __('Primary Footer Menu')
        ));
?><?php
// I'm enabling featured images here
        function addThemeSupport() {
            add_theme_support('post-thumbnails');
        }
        add_action('after_setup_theme', 'addThemeSupport');
?><?php
// Customizing the excerpt
        // remove the [...] from the excerpt
        function new_excerpt_more( $more ) {
            return ' ';
        }
        add_filter('excerpt_more', 'new_excerpt_more');
?><?php
// Replacing parentheses from category post counts with a span
        function replace_post_count_parentheses($cat) {
           $cat = str_replace('(', '<span class="count">', $cat);
           $cat = str_replace(')', '</span>', $cat);
           return $cat;
        }
        add_filter('wp_list_categories','replace_post_count_parentheses');
?><?php
// custom excerpt lengths depending on page
        function isacustom_excerpt_length($length) {
            global $post;
            if ($post->post_type == 'post')
                return 32;
            else if ($post->post_type == 'uncategorized')
                return 20;
            else if ($post->post_type == 'entries')
                return 75;
            else
                return 80;
        }
        add_filter('excerpt_length', 'isacustom_excerpt_length');
?><?php
// If more than one page exists, return TRUE.
        function show_posts_nav() {
        	global $wp_query;
        	return ($wp_query->max_num_pages > 1);
        }
?><?php
// removing the P tags from around post content images
        function fb_unautop_4_img( $content ) {
            $content = preg_replace('/<p>\\s*?(<a rel=\"attachment.*?><img.*?><\\/a>|<img.*?>)?\\s*<\\/p>/s','<figure>$1</figure>',$content);
            return $content;
        }
        add_filter( 'the_content', 'fb_unautop_4_img', 99 );
?><?php
// adding the current menu item when on single page
        function add_custom_class($classes=array(), $menu_item=false) {
            if ( is_single() && 'Home' == $menu_item->title &&
                    !in_array( 'current-menu-item', $classes ) ) {
                $classes[] = 'current-menu-item';
            }
            if ( is_category() && 'Archives' == $menu_item->title &&
                    !in_array( 'current-menu-item', $classes ) ) {
                $classes[] = 'current-menu-item';
            }
            return $classes;
        }
        add_filter('nav_menu_css_class', 'add_custom_class', 100, 2);
?><?php
        function empty_content($str) {
            return trim(str_replace('&nbsp;','',strip_tags($str))) == '';
        }
?><?php
// making the archive pages have unlimited posts
        function wpd_testimonials_query( $query ){
            if( ! is_admin()
                && $query->is_category()
                && $query->is_year()
                && $query->is_archive() ){
                   $query->set( 'posts_per_page', -1 );
            }
        }
        add_action( 'pre_get_posts', 'wpd_testimonials_query' );
?><?php
// adding the date to the main menu and linking it to something
        add_filter('wp_nav_menu_items','add_date', 10, 2);
            function add_date($items, $args) {
                if( $args->theme_location == 'primary' )
                return $items . '<li class="navdate"><a href="https://www.timeanddate.com/on-this-day/">' . date("l F jS, Y") . '</a></li>';
            return $items;
        }
?>

I invite anyone to help me revise anything in my functions file. If you see anything that can be more bullet-proof or a better way of writing something, please please please do it!

Oh, and just FYI, I added individual php tags to better differentiate each function. I'm old, what can I say!