By default, WordPress runs background tasks on occasion when pages are visited. This can lead to scheduled posts appearing late. If you’d like to set up a real cron job for WordPress, do the following:
Add the line:
*/15 * * * * wget -q -O - http://yourdomain.com/wp-cron.php?doing_wp_cron >/dev/null 2>&1
Also, edit wp-config.php, and add the line:
This will run WordPress’ background tasks every fifteen minutes regardless of when site visits occur. And, it turns off the process that runs on occasional site visits – which is unnecessary if you have a cron job.