There are several ways to notify your employees about upcoming birthdays.
First to set up the settings you need to click on the settings button on the dashboard, you can find it on the panel of "Upcoming birthdays".
On the dashboard view you can set how many days in advance the birthdays are shown.
Here you can decide if employees get notified about the birthdays and at what time they get an e-mail. The e-mail shows the birthdays that are on this day.
Administration settings give you a little bit of an easiness. The system can notify selected employees an X days in advance. That gives an opportunity to organize flowers, candy, gifts and you'll never forget a birthday again. :)