Last update date of posts + Suggestion

Hello great Catchthemes team i want to insert the last update date of posts on my blog and i follow the first method here http://devotepress.com/tutorials-hacks/display-last-updated-date-wordpress/ when i add this code (as described on devotepress) on my functions.php i get error 500 on my blog, simply this code broke the blog with catchbox pro 4.9.3 i get blog back with backup of functions.php is there any method to put this option on catchbox pro and make it working in the next theme version? Maybe an option to add or remove "last updated post". I think its a great idea for all users to see updated post expecially when you have so much readers and you update article 2 times a month like me. It is difficult to keep track of updated articles and having this option to show you when you have modified an article the last time would make blogging so much easier.