There is an option that can be selected to change the period that the posting goes against, follow the below details:
Open the Administrator Desktop and select the Billing Configuration.
Select Legal Aid Settings on the left hand side.
There is a section that states Assessed Claims Manager.
There are 3 options Work Concluded date/Receipt Date and Current Period.
If you want the period to change dependent on the the date you put in the posting you will need to select Receipt Date.
Select Apply and then OK.
Log out of Access Legal Fusion and back in this should have the new setting applied.