A free app for Android, by Caros2.

This application was designed to help you manage your day-to-day schedule and plans more efficiently. It allows you to input and manage your personal schedules and plans on different calendars. You can also add special days such as birthdays and anniversaries. 

If you are looking to make an appointment or plan for a specific day, the Caros Calendar app has a calendar function that lets you do this. You can also add to-do lists. The calendar can be customized with colors. This app has an anniversary function that lets you manage your birthday and special day. You can also send reminders.