Yes! You can create an extension after an assignment due date and time has passed, and, in most cases, do the same for assessments (quizzes and tests). Note you can choose a new extension date, but the extension time will default to 11:59 pm local time. You can find instructions on providing extensions here.
If your student hasn't yet started their assessment, or if they have remaining attempts, you can give them an extension.
If a student has already completed all their attempts on their assessment and you want to let them to retake it, you can either add additional attempts for the individual student using these instructions or reset the assessment to let them back into the assessment. Either reset only their last attempt to give them one more try, or repeat the reset process to allow them multiple retakes. Please note resetting the attempt will delete previous assessment data.
For more information on resetting assessments, check out this article.