Update: I also added this mysql command
INSERT INTO wp_postmeta (post_id,meta_key,meta_value) SELECT id,'_pingme','1' FROM wp_posts WHERE MONTH( post_date ) = MONTH( CURDATE( ) ) AND DAYOFMONTH( post_date ) = DAYOFMONTH( CURDATE( ) ) AND post_status = 'publish'
From what I understand, the next time a page is loaded, the rows added by this command which include the _pingme field will trigger a ping. Am I correct?