Calendar events for past 5 years gone suddenly

Quick update, they were able to sort this out. Come to find my calendar had been using Gmail and it was toggled off for some reason.

settings > apps > calendar > calendar accounts and see if you have any calendar disabled, if so enable it and recheck your calendar for missing events.

This was the solution to my issue and maybe it could help you.

The calendar is the app on my iPhone/iPad/Macbook which has been used for years and I have never once been prompted to sign in or use an account. To my knowledge the only account used was the one associated with my appleid.

This is my understanding of what iCloud provided:

"iCloud helps keep your data safe in two main ways: syncing and backing up. For example, if you're using iCloud Photos, iCloud Drive, or Notes, your information automatically syncs to the cloud and is kept up-to-date across all of your devices whenever you make a change."

There is also a section under settings > account > iCloud > iCloud Backup which backs up your phone.

So I am at a loss as to why my past 4 years of events I had stored in my calendar have suddenly gone missing when I have not done anything on my end to remove them, they simply are just not there anymore.

Thank you for sharing a similar experience. It's unfortunate this happened, in the 20 years of my owning and using Apple products this is the first for me where I have actually lost data using iCloud/Calendar. The restore points for iCloud also are no help as the events are also gone despite having these events through a 4 year period, now suddenly they are just gone.

The larger question / concern is how did this regress. Was a regression introduced via a new iOS update? It is unknown as no settings were changed/modified. If no notification of such a regression being introduced is made to the user, it makes troubleshooting difficult. Thankfully the labyrinth of settings that is now iOS was easier to navigate with the help of Apple support, though I recall earlier times when "it just works" was actually a thing.

I did the same but they were not able to recover my data after speaking with them unfortunately.