Burden Structure change mid year

In Oracle Project Costing, version 12.2.9, we need to create a new structure to be effective mid fiscal year.

We usually then adjust our rates later in the year. My question is, will the rate change be effective back to the first day of the fiscal year, (which is what we prefer), or will it only be effective to the first day of the new structure? Or do we have to change the rates in both the old and new schedules?