Unable to Modify a Voucher's GL Date

We are trying to edit a voucher's GL date. However, when we save the changes, the date is reverting back to the original date. The voucher hasn't been paid or approved, so why won't it let us change the date?

Vouchers do not allow the date on the line items to differ from the GL date on the Voucher Setup tab. Therefore, when attempting to edit the GL date on a voucher, make sure you check the "Move all line items to new G/L date" box on the Voucher Setup tab:

Once you do, you can click Save to move the date.