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.