- Make sure Edit mode is ON (top right of screen)
- Then go to Assignment Dropbox in the left hand panel
- Select dropdown menu next to the Turnitin assignment you want to edit
- Select EDIT
- change due date
- change post date
- then save
However, if you want to just accept late papers and not change the due date:
- in the screen where you can change the due date, select More Options
- scroll down to the option that says Accept Late Submissions? Switch to yes
- and Save
see screenshot below (click to enlarge)
