As you migrate your course from semester to semester, you might want to “shift” all dates (or a number of dates) forward in a certain way without having to edit assignments one by one.  You can “batch edit” these dates in “assignments.” Check this tutorial for some instructions.

Tip: If you are not sure exactly how many days forward (30 days or 31 days?) to shift, I would encourage you to choose the smaller number (30, rather than 31, for instance) as it is easier to batch edit again to shift one day forward at a time, but Canvas does not give the option to batch edit dates back.