OK, but that does cover most of the first section of my suggestion - all the stuff about connecting to the database and running a query is already done for you. So my suggested first step is to modify the query to retrieve the creation time and just display it somewhere on the page.
I understand that you have no background in PHP, but I presume if you’re looking after this site with a view to modifying it, you are intending to learn some PHP. So as you already have code that does connect to the database, run a query and do something with the results, you’ll be able to read through that code and, along with the PHP documentation, figure out which bit does what.
As for the comparison, @John_Betong makes a very good point. As you seem to be storing the creation time as a string rather than any of the date/time column types, it may make things more complex. So if you’ve only just added that column, now would be a good time to make the change.