On Appogee HR you can create notifications based upon date fields on the user profile.
A notification can be set to remind an employee that a probationary review is due by undertaking the following steps:
Go to Reporting > HR Notifications.
Under Employee Profiles, go to Relative Date Notifications.
Select employee start date as the trigger, and the date options to be 3 months after, choose who should be notified, and add a notification email message.