Multiple Calendar entries on iPhone 15 and iMac after backup sync

This massive duplication issue usually happens when a local backup syncs and conflicts with existing iCloud data, creating an infinite loop of identical entries. Since deleting them manually is impossible, here are the most effective ways to batch-remove or merge them:

• The iCloud Toggle Trick (Easiest):

1. 1. On your iPhone, go to Settings > [Your Name] > iCloud > Show All > Calendar.
   2. Toggle the switch to Off.
   3. When prompted, choose "Delete from My iPhone" (don't worry, your core data is safe in the cloud).
   4. Restart your iPhone, go back to the same setting, and toggle Calendar back On. This forces the phone to download a clean sync from the server, often discarding the local duplicates.

• Mass Delete via Mac Calendar App: If you have a Mac logged into the same iCloud account, open the Calendar app. It is much easier to manage mass data there:

1. 1. Click Calendars in the top-left corner to see your list.
   2. Look for duplicate calendar categories (e.g., two "Home" or two "Work" calendars). If you find a duplicate calendar that contains the spam entries, right-click it and choose Delete.

• Use a Dedicated Cleaner App (Fastest for years of data): If the duplicates are all baked into a single calendar layer, searching manually won't work. Download a highly rated utility app from the App Store like "Delete Duplicates" or "Calendar Cleaner". These tools can scan your entire calendar database, detect identical events spanning back years, and let you delete thousands of duplicates with a single click.
• Check Third-Party Accounts: Go to Settings > Apps > Calendar > Calendar Accounts. Ensure you didn't accidentally log into the same Google, Outlook, or Exchange account multiple times, which overlays identical schedules on top of each other.