In Microsoft Planner, once your task has a start or due date, you can see it on a calendar either in Planner using Schedule view or in Outlook by adding your plan to your Outlook calendar (coming soon).
Use Schedule view to see tasks on a calendar
After you add tasks in the Board view of Planner, you can see those that have start or due dates by choosing Schedule at the top of your plan.
You can then grab the right end of any task to stretch it over two or more days.
Tasks that don't have a start or due date yet are listed to the right of the calendar in the Unscheduled tasks list. Drag these tasks onto the calendar to quickly add due dates.
You can sort the Unscheduled tasks list by Bucket, Assigned To, Progress, and Category using the Group by drop-down above the list.
If you want to remove a task from the calendar, you need to remove the start and due dates from the task. Open the task, and delete the contents of the Start date and Due date fields.
See your Planner calendar in Outlook (coming soon)
If you want to view your Planner schedule in Outlook, first the plan owner needs to add the plan to the Outlook calendar with an iCalendar format feed, and then each member can add the plan to their Planner calendar. This feature will be coming to your organization's Planner soon; watch this article for details about how it works.