Hello

function scheduling_per_season(){
?>
<script>
  var currentTime = new Date();
  var month = currentTime.getMonth() + 1;
  var imglocation = "/wp-content/uploads/season-images/";  // put the images in this folder

	switch(true) {
		case (month >= 6 && month <= 8):
			var seasonImg = "summer.jpg";
			var season = "summer";
			break;
		case (month >= 9 && month <= 11):
			var seasonImg = "fall.jpg";
			var season = "fall";	  
			break;
		case (month == 12 || month == 1 || month == 2):
			var seasonImg = "winter.jpg";
			var season = "winter";
			break;
		default:
			var seasonImg = "spring.jpg";
			var season = "spring";
	}
  	document.getElementById('changed_on_season').style.backgroundImage = 'url(' + imglocation + seasonImg + ')';
	document.body.classList.add(season);
	document.getElementById('changed_on_season').getElementsByClassName("av-special-heading-tag")[0].textContent = "It is "+season+" and:"; 
	
</script>
<?php
}
add_action('wp_footer', 'scheduling_per_season');