Click the "Assignments" tab.
Click the gear icon next to the assignment you wish to edit.
Click More Options.
Scroll to the bottom of the page and edit the dates. You can also set the "Available from" and "Until" dates if you want to limit the assignment to a specific time-frame. Please do not use "Available from" or "until" for Turnitin assignments!
Click Save when finished.
Note that it is also possible to utilize the course Calendar to set due dates for an assignment, as displayed below:
For more information on utilizing the Canvas Calendar please see How do I use the calendar as an instructor?
Canvas allows for accommodations for individual students, in instances where they have special permissions or had technical errors. For information on how to add accommodations see Allowing Accommodations for Assignments and Quizzes in Canvas.