HI @xfang1
In Canvas, a due date is understood to be when work is meant to be completed and/or submitted. Changing that up, in my opinion, would be confusing.
However, in Canvas, due dates don't stop students from accessing activities or submitting work. The availability dates do that. So, you could set the due date to the time you want students to begin the quiz and then set the available dates for when you want to cut off access to the quiz. Note, I think this will trigger late submission responses for each student submission to the quiz. As it's not how Canvas was designed to work.
The only way I know to remove the automatic calendar entry would be to remove any due and available dates on the quiz. You could then create manual calendar events for when you want students to start the quizzes.
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