If you need to adjust the due date on an assignment, you can do so in your Assignments sub-tab.
Click on the Classes tab, choose the class and click the View Class button.
Select the Assignments sub-tab.
Click on Actions next to the assignment that you wish to adjust.
Select Settings.
You will be brought to the first page of the assignment creation process. Click Next.
On the Assignment Settings page, adjust the due date.
Click Submit to finalize your update.