My Calendar app is configured to read more than one calendar (iCloud, Google, Exchange). If I create an event from my computer, it won't be visible on all other calendars, and if I create an event on any of my iOS devices I cannot see on the Mac Desktop Calendar.
I tried to remove Calendar from iCloud Settings on my Mac but, I did not get any luck.
Best Answer
First, check your iPhone:
For iCloud Calendar, check whether it is enabled on both devices under
Settings > Apple ID > iCloud
For Google, check whether Fetch New Data is set to Push in
Settings > Passwords and Accounts
and also under Gmail look, whether is it enabled or not.For Exchange try the same.
Now check the same settings on your mac.