Iphone/Mac calendar sync

This appears to either be a bug or an undocumented feature. Either way, Apple don't seem to care about it, as they want everyone using iCloud.

iPhone Calendar no longer syncs with Mac … - Apple Community

https://forums.macrumors.com/threads/iphone-calendar-no-longer-syncs-with-mac-vice-versa-direct-syncing-not-icloud.2391500/

I have the same issue as MrPerdu,

I dont use iCloud and the info tab redirects me to use iCloud. Very frustrating

Hello MrPerdu,

On both your devices, turn off Calendars in your iCloud settings, wait a few minutes and turn it back on.

If you synch your iPhone on your Mac using Finder, connect your iPhone to the Mac, select your iPhone in Finder, go to the “Info” tab and make sure Calendars is selected.