Wanting to change accounting periods from 12 to 13 for financial statement adjustments

We are considering changing to 13 periods.  We currently use 12 periods and utilize only General Accounting & Accounts Payable components of JDE.  We want to do this to isolate audit adjustments to a separate period to avoid impacting other users and to separate financial reporting activity.  Have reviewed written help but does not indicate what all is impacted by such a change.  Indicates that I must change closing date of Period 12 to 6/29/2013 & assign 6/30/2013 to Period 13.  Does this mean I either have to close the fiscal year 1 day early for all users (alot of