iOS 13 Reminders app incompatible with macOS 10.14 and earlier
If you have iOS devices and an iPad or Mac you’re going to want to read this Apple Support article regarding the new Reminders app before you upgrade to iOS 13. This may save you a lot of frustration.
Upgraded reminders aren’t compatible with earlier versions of iOS and macOS. If you upgrade your reminders on your iPhone with iOS 13, your iPad and Mac using the same iCloud account can’t access your reminders until iPadOS and macOS 10.15 Catalina are available.