Calendar problem

Hallo James! On your iMac go to System Preferences > iCloud, and make sure that Calendar is checked as on. On your iPhone go to Settings > Your Name > iCloud, and make sure that Calendar is checked as on here as well. And as dialabrain has posted, both iMac and iPhone must be logged into the same iCloud account.

Depending on how many entries you have in your iPhone Calendar it might take some time to synchronize with your iMac. On any browser you can go to iCloud.com and check that your calendars have synced. Hope this helps you! Regards, Ian.

I don't have an iPhone but I would think if both are logged into the same iCloud account they would sync.