Is it possible to change Mileage Determinant month on an active policy/expense template?

Summary:

The current setup has the mileage determinant calculating cumulative mileage from January to January. However, it needs to be changed to April to April. I have tried end dating the the current determinant and setting up the new one. Also, refreshing the end date and start date of the policy rates and activating them,. When testing it is still pulling the cumulative mileage from the old Jan - Jan range.

Is there an easy method to change this, or, does a brand new policy need to be made and associated to the expense type to make this happen?