MacOS Calendar App repeats all annual events on a DAILY basis when syncing iPhone to MacBook Pro
This is an issue posted by otherness2018 in August 2023. A dozen other people noted that they have the same problem
This has been happening for me at least 18 months.
When synching iPhone to MacBook Pro, even though both operating systems are always up to date, my annually repeating events on my MacBook Pro change to repeating DAILY. Now I have hundreds of events showing up on EVERY date on my MacBook's calendar. It takes hours to clean up. (The iPhone calendar remains as it should be.)
MacBook Pro 16″, macOS 15.0