getting database syntax error

WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''YEAR') < CURRENT_DATE() LIMIT 50' at line 1 for query SELECT BLOG_ID, ID FROM wp_network_posts WHERE DATE_ADD(post_date, INTERVAL 1 'YEAR') < CURRENT_DATE() LIMIT 50 made by do_action_ref_array, call_user_func_array, postindexercron->process_tidy_agedposts, postindexermodel->remove_posts_older_than