Inserting addiitonal rest days?

Say I have a training plan that gives me one "Day Off" per week. But due to whatever ... I want to insert at some point one (or two) additional "Days Off" without taking them from the regular scheduled program ... so essentially I want to insert an additional day into my program during one particular week? I realize that that would push all dates back by one day.

Is that possible? How is that done?