Calendar resetting to wrong date and time, always at 11pm
My wife and I have a strange thing happening. Suddenly some, though not all, of our shared calendars are resetting appointments for different dates and always at 11pm. We have an old iMac (2012), 2018 iPad Pro, 2019 MacBook Pro 16 inch, 2018 MacBook Air, iPhone SE, iPhone 11, Apple Watch 6 and Apple Watch 3.
We did all the usually resetting up times and timezones... Ideas? What are we missing here? Thanks!
iPhone SE, iOS 14