The Test

Without JS the button points to the RSS feed. This serves as a placeholder. The button was most likely copied and pasted.

Upon page load the website makes a call to the /rand.php endpoint, which returns a date in ISO8601 format. That is then used to produce the actual link.

    
                <script>
        $.get("/rand.php",function(data){
            $('.cc-navaux').attr('href','https://www.smbc-comics.com/comic/' + data);
        });
        </script>


  

(lines 172ff. of the HTML source) Why? Ask the author.