Birthdays and anniversaries are probably the most common reminder, so lets start by entering a yearly event. Click the Edit button from the Reminders Window, then click the Add button from the Events Editor. You will see the following input fields:

Type in the name for the event. If you want to track the number of years, add the original year enclosed in < and > like "Megan's <1978> Birthday" and when your reminder comes up, it will list the event as "Megan's 30th Birthday".

Enter the date in mm/dd or dd/mm format (following your regional date setting) and enter the number of days advance for your countdown to begin. When you're finished, click the check button to save or the X button to cancel.