You can change Open Dates, Due Dates, and Answer Dates for each student individually.
Giving a few students an extension on a single assignment
From the Homework Sets Editor, click on the fraction in the “Edit Assigned Users” column corresponding to the assignment.
Click on “Edit data for __” for each student to whom you wish to grant an extension.
Under General Information, change the Open Date, Due Date, and/or Answer Date as needed. If you change a date, be sure to click the checkbox to its left.
Click “Save Changes”.
Giving one student extensions on many assignments
From the Classlist Editor, click on the pencil next to the username of the student to whom you want to grant extensions.
On the page that appears, click again on the username of the student.
Change the Open, Due, and Ans dates as needed. If you change a date, be sure to click the checkbox to its left.