The option to edit the dates on your imported bank transactions isn't available after the import process. Let me provide you a workaround for it.
You'll have to exclude these transactions first. Here's how:
Click the Banking tab.
On the Banking page, select the For Review tab.
Tick the checkboxes of the transactions with incorrect dates.
From the Batch actions drop-down, select Exclude Selected.
Once that's done, you can edit the dates of your CSV file before importing it again. Ensure that your CSV file only consists of those transactions that you've excluded earlier so you won't have any issues with duplicates.
When all of this is wrapped up, you can proceed to reconcile your bank account to make sure that everything's in order. View this article for more details: Reconcile accounts. You'll find the steps starting from the setup up until the reconciliation process itself.
Drop me a comment below if you have any other questions. I'll get back to you as soon as I can.