If you have a student that needs extra time to complete an assignment (e.g., joined the course late, excused absence), you can override the deadline for that student for a particular assignment. To do this:

1. Navigate to the Assignments panel on the course home page.
2. Click to select the particular assignment.
3. Click Extend deadline for a student.
4. Click Add deadline override, select the student from the list, and enter the new deadline.

You can even extend deadlines after the fact; Perusall will always recalculate scores to make them consistent with your current assignment settings.