Creating task in other user calendar

I use the ability to add tasks for other employees from their calendar in Asana.
In turn:

  1. searches for an employee in the search engine,
  2. I go to his task list,
  3. I select the ‘Calendar’ tab and on the right day I click on the free field and add the task.

The problem is that for some employees it is possible to do so and for others adding tasks is inactive. You cannot click on a day to add a task.
What it depends on? Are there any permissions for this?