If you run the Divi theme then you likely have edited the footer credit text via footer.php. The problem then is when the theme is updated, the footer.php file over-written and you have to re-edit the footer credit text.

1. Go to Divi Theme Options
2. In the box "Add code to the < body > (good for tracking codes such as google analytics)"
3. Add the following code (edit the red to suit)

*UPDATE: there is now a better way to do this with the latest version of DIVI, please see the end of this post for instructions. 

UPDATE: thanks to Lorenzo Novaro for providing a better version of this code that will keep your styling in tact:

Please use this code:

<script type="text/javascript">
jQuery(document).ready(function(){
jQuery("#footer-info").replaceWith('<p id="footer-info">Copyright <?php echo date("Y"); ?>. Designed by <a href="http://www.cssdorks.com" target="_blank">cssDorks</a></p>');
});
</script>

This is the original code snippet. 

/*change footer*/
<script type="text/javascript">
jQuery(document).ready(function(){
jQuery("#footer-info").text(' ');
jQuery('<p>Copyright <?php echo date("Y"); ?>. Designed by <a href="http://www.cssdorks.com/divi" target="_blank">cssDorks</a></p>').insertAfter("#footer-info");
});
</script>

 

Editing this in Theme Customizer is now the best way with the latest version of DIVI. This is pictured below. You can enter this text to automatically update the year: <?php echo date("Y"); ?>  Company Name, Inc. All Rights Reserved.