Right-click the task you want to delete, then click Delete from the drop-down menu.
Click in the confirmation message to accept your deletion.
Deleting a task in the Month view
Tick the checkboxes corresponding to the task you want to delete, then click
on the Month toolbar.Click OK in the confirmation message to accept your deletion.
Note
For shared or group calendars, you can only delete their tasks if you have the Edit permission on these calendars.