Why do some contacts have double birthdays? - day-by-day-calendar/feedback GitHub Wiki

Birthdays in our app are taken from two sources:

• Special calendar “Birthdays and events of contacts”;
• Address book on your device.

You can easily discover the source by clicking on the birthday you are interested in: it opens, and you see if it’s a special calendar or address book contact. You can turn off calendar “Birthdays and events of contacts” in app settings or turn off the option “Show birthdays”. If you turn off the latest, birthdays from your device address book won’t be visible. If you keep your phone in hand, a more preferable way would be the first one. It would show birthdays from your address book. Press “birthday” and you’ll be able to open contact, give a call and congratulate your acquaintance.

Please see the screenshots to check double holidays as well: