Thanks for all the feedback. I believe I now have it figured out.
I added a column to the table and named it DateAdded with Type - TIMESTAMP, NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP. The comparison you suggested now seems to work in that it does not delete rows that were placed in the table today. After a couple of days I will change the INTERVAL to 2 or 3 days and see what happens when I try the query in the Mysql client. I still have a column named 'Posted' which contains a date in simple English, i.e. Month Day, Year.