Edit AR Invoice Date

Hello, I recently posted about 10 invoices from BL with the invoice date of 1/20/2014.  Is there an easy way to change or edit this date in AR, without having to void the invoices and regenerate all 10 from BL? When I go to adjust the invoice in AR, the invoice date area is greyed out and I cannot make any edits.

Thank you!

DeltaAK