Birthday Calendar is a free and open-source Android application that helps you keep track of all the upcoming birthdays and anniversaries of your friends on social networks. The app supports all the apps that sync contacts with your Android device, including many social network and messaging apps. You can enable reminder alarms and decide which contacts you want to see. The app also allows you to customize your experience for tablets.

The app has a simple interface that displays a list of upcoming birthdays and anniversaries for all your friends in all your social networks. You can choose how you want to get notified, whether it's on the same day or one day in advance. Additionally, you can pick any calendar color you like to personalize your experience.

Birthday Calendar is a great app for anyone who wants to stay on top of their friends' birthdays and anniversaries. Best of all, it's available for free, and it's open-source. Head over to Github and fork BirthdayCalendar to contribute to the project.