Fiscal Period Setup Error "The date cannot be part of a different fiscal year"

Confirm there are no fiscal years setup with incorrect dates in the same Fiscal Period window.

Then run Reconcile in Admin for Fiscal Periods. (Microsoft Dynamics GP>Tools>Utilities>System>Reconcile, then select Fiscal Period and insert into the list)

The report will tell you where there were errors, go back to the Fiscal Period window and fix the corrupt year, then create the new year.

You will then be required to run a reconcile on GL, AR and AP.