There are steps how to do so. In particular
Share a calendar with specific people
On your computer, open Google Calendar. You can’t share calendars from the Google Calendar app.
On the left, find the “My calendars” section. To expand it, click the Down arrow Down arrow.
Hover over the calendar you want to share, and click More More and then Settings and sharing.
Under “Share with specific people,” click Add people.
Add a person’s or Google group’s email address. Use the drop-down menu to adjust their permission settings. Learn more about access permissions.
The recipient will need to click the emailed link to add the calendar to their list. Learn how to add someone else’s calendar.
Unfortunately the recipient did not receive any email.
The other ways to add other calendar are. But subscribe to calendar works only to my personal calendar. And I do not find correct URL to use to let other to subscribe to my other calendar.
Could you suggest how to give permission of my gmail calendar to other gmail user?