Originally Posted by nastynun

wp-cron-future-pings: suppresses the default ping and trackback action when you post a new item dated in the future. Then (roughly) every 15 minutes the plugin checks to see if any future-dated posts are now visible to readers. If they are, the pings and trackbacks are sent

http://www.skippy.net/blog/2005/05/26/plugin-wp-cron/