Virus

If running iOS 13 or earlier versions, check: Settings - Passwords & Accounts - Accounts - Any rogue entries here? If so, delete the rogue account. 

If running iOS 14, check: Settings - Calendar - Accounts - Any rogue entries here? If so, delete the rogue account. 

The Apple support article is below. 

https://support.apple.com/en-us/HT211076

This is a common calendar spam hack - you somehow subscribed to a calendar that's adding all these 'events' to your calendar, and exploiting the calendar reminder feature to trick you into thinking your device has a virus.

The fix is simple - just unsubscribe from the calendar and it will all go away.

https://support.apple.com/en-us/HT211076

Click here and remove those calendars.

(197916)