Calendar events disappeared after updating iPhone to iOS 18.5

I am going through this right now too. I have tried everything and contacted Apple multiple times. Right now, I am currently using an old device to see if I can use an older iCloud backup to get the events back. I tried one backup, and it didn’t work, so I am working on another older backup to see if that will work. If not, then I have no other options. There was no restore backup on iCloud.com for the calendar either; it seemed to have deleted as well. There was definitely a glitch in their recent update, as I have checked on Reddit, and Apple said a lot of users are contacting them about this. I use my calendar for everything, and it’s all gone.

Update to my last response. When I backed up to my older iCloud backup from 6-12-25 the calendar events are back. I just need to figure out how to get them to my original phone without having to reinstall everything.