Explanation
If you use unified interface, you can display any record in a calendar view via the calendar control.
Go to Settings->Customization->Customize the System
Open the configuration for the entity that you want to use the calendar control (Opportunities in our example) Click the View tab Click "Add Control" and select the calendar control.
Click the dot for every interface from which you want the calendar control to be available.
Reference:
https://crmtipoftheday.com/1206/view-any-dynamics-365-record-on-a-calendar/