Birthdays into Calendar is a free, easy-to-use app that allows you to add birthdays, anniversaries, and other important dates from your contacts into your favorite calendar app. Compatible with all calendar apps available for Android, including Google Calendar, Samsung Calendar, and HTC Calendar, this app is designed to seamlessly integrate with your device.

Unlike other birthday reminder apps, Birthdays into Calendar is the only app that integrates with Android's calendar database. This means that you can view all of your contacts' birthdays as events in your favorite calendar app without having to switch between multiple apps.

The app also includes a color picker for the birthday calendar, event reminders, and the ability to filter contact events based on account. If you want to try the app before purchasing the full version, there is also a free version available for download on the Google Play Store.

It is worth noting that there are known bugs with the app, including reminder issues with Android 2.3 and a bug that causes the app to disable after reboots on devices with Android 4.1 or all versions of Samsung Galaxy S4. However, there is a workaround available for the latter issue.

Overall, Birthdays into Calendar is a useful and practical app for anyone looking to keep track of important dates.