As teacher, create a quiz and set a time limit and set When time expires to "There is a grace period when open attempts can be submitted, but no more questions answered". DO NOT set an end date. Set Submission grace period to a suitable amount of time to let you do the tests below.
1. As student, start a quiz attempt and answer some questions. Then leave the browser tab open until time expires.
2. You will be automatically redirected to the review page, and the quiz will move into the overdue state. There will be a clear statement of when the deadline to submit the quiz is.
3. Click the submit button, and your attempt will be submitted and counted.