Hi Dusan,
It is possible to show a calendar as an embedded report on a form. First you want to make sure you have a calendar in that child table that is set up to display information in the way you want it and with any filters you might need. Then when you look at the embedded report on the form you would want to edit the form element that corresponds to that report. You can do that by right clicking right at the edge of the report or by customizing the form.
Within those options there is a place to change the report being used to display records and you can select the calendar report from the dropdown.
Then once you save the form you should now see your calendar report where your embedded report once displayed. I hope this information is helpful.