Sync Calendar Events across all devices iPhone / iPad / Mac

The calendar does not sync between devices. All the devices sync with the email client server which hosts your calendar. Add the email account which hosts your calendar events on all the devices.

Where are the calendar events stored on your iPhone? Please add the email account, that's it.

See the iPhone and Mac Calendar Pics below

When you add events to the Calendar it gets added to the Default Calendar set on your device.

See the pic below