Check out code below.
Function returns a number of posts published with todays date. You just have to modify a navigation a little bit to add this number counter to a menu bar.
echo "<h1>Today is: " . date("Y-m-d") . "</h1>";
function published_today() {
$counter = 0;
$posts = get_posts(array('numberposts'=>-1));
foreach ($posts as $post){
if (get_the_time('Y-m-d', $post->ID) === date("Y-m-d")) {
$counter++;
}
}
return "Posts published today: " . $counter;
}
echo published_today();