Configuring When Your Daily Cron Runs
Begin by logging into the WHMCS Admin Area.
Go to Configuration > System Settings > Automation Settings, or, in WHMCS 7.10 and earlier, navigate to Setup > Automation Settings.
In Time of Day, choose the hour of the day you wish for the daily automated actions such as invoice generation and recurring billing to be performed.
The tasks will execute the first time the cron is invoked by the web server during the specified hour.
Important Note: The cron must be configured to run at least once in the hour you specify here within your web hosting control panel's cron task setup. Failure of the cron to be invoked during the hour specified here will result in cron tasks not executing.