Currently, you are unable to make a change to recurring shifts without changing past published shifts. It would be a much more useful feature if you could modify the recurring shift as of the date you are modifying it and not before. 

For example, if my employee works every Tuesday from 7-3 and then we decide that two weeks from now, he will be working every Wednesday from 7-3, I should be able to go to the schedule of two weeks from now and modify the recurring shift to be Wednesdays, from that date forward. As the app works right now, I am able to make this adjustment, I am even able to say that as of a specific date, this shift will occur on Wednesdays. But when you click save and have a look at the shifts existing before that date, it's been changed to Wednesdays, as though you never modified the shift to change to Wednesdays only from a specific date. 

What I propose is another field that says 'apply change as of' (date).