I have a calendar app on my iPhone, which always displays a duplicate birthday calendars. This issue also affects my iPod and iPad.
Here are some solution, you can make a try to resolve it.
Solution 1: Refresh calendar list
- Open calendar app
- Click on a calendar in the middle bottom of the screen.
- Swipe down to refresh all calendars that help to remove the duplicated birthdays calendar.
Solution 2: Using Decipher backup repair
- Install Decipher backup repair
- Backup your iPhone or iPad in iTunes.
- Run the custom version of Decipher backup repair to create a “Decipher repaired” backup.
- Restore “Decipher repaired” backup.
SEE ALSO: How to Add, Remove US holidays from iPhone calendar
Solution 3: Merge to iCloud
- Select a location to store your contacts and move it.
- To merge to iCloud,Open Settings > Mail,Contacts,Calendars > iCloud
- Turn off Contacts and click “Delete contacts from my iPhone”
- Wait until it syncs and check whether the calendar has gone by opening calendar app
- If it doesn’t work, again turn On your contacts and wait
- The duplicate calendars would be gone.