This could be done if you have just one Table for everybody’s tasks. There is no need to have a separate Table for each person’s tasks. Just create a single Tasks table, and in that table make sure to have a “Collaborator” type field where the person each task belongs to can be defined.
Then, instead of each person working in their own Table, you create VIEWS within the Tasks table, one for each person. So each person works within their own View, which filters to show only Tasks where “Collaborator” = that person.
With that setup, all of the Tasks would be in one table, and so the Calendar View of that table would include everyone’s Tasks.