PO was received and vouchered for wrong year 2015 G/L Date

Need to fix a PO receipt/vouchered match type 1 and 2 for which a wrong year was entered in the G/L date

The transaction date is 01/05/2015

The G/L Date was entered incorrectly as 01/05/2016.

The G/L date should have been 01/05/2015.

Both 2015 and 2016 periods are closed.

Summary:

Need to know how to correct a PO for which the wrong year was entered as the GL  date. 

Is a reversal possible for this, since its a closed period? If not, how should  go about correcting this so that the favorable  PPV should show in the 2016 PPV reports?

Thanks - Debbie