Due dates on projects can change depending on various situations. In a scenario that occurred with us, the need for the completion of a project was escalated so the Due Date was pushed up.
However, this project had a number of tasks associated with it that still had Due Date set to later than the new Project Due Date. As this was the case, the new Project Due Date could not be saved.
It would be nice to have the ability to automatically update all existing Task Due Dates when the Project Due Date is changed to an earlier date.