Calendar events missing from old Apple ID
I had a calendar associated with an old appleid email that I can no longer can access and all the events have disappeared.
iPhone 15 Plus, iOS 26
Question marked as
When you remove or log out of an old Apple ID, its associated iCloud calendar data is disconnected or removed from the device. To recover these events, you must recover access to that old Apple ID account, sign back into it, or export the data from a device that still has it cached.
If you no longer have access to the email, you might need to enroll in account recovery
How to use account recovery when you can’t reset your Apple Account password - Apple Support