You'll need to undo the reconciliation to edit the ending date, Zed.
To undo the reconciliation, we have two options: you can either manually un-reconcile one transaction at a time or ask your accountant to do it if you want to undo the entire period.
After transactions are unreconciled, you can now redo the reconciliation process together with your updated ending date.
- Go to the Gear icon, then click Reconcile.
- Select the correct account.
- Enter the correct Ending Date and Ending Balance.
- Complete the reconciliation.

I've included an article that will assist you with reconciliation issues: Fix issues when reconciling accounts.
Please visit us if you have any further questions, and we will be glad to assist you again soon.