Hi there, @SPC220. Thanks for reaching out and providing detailed information about your concern.
You're correct about the process of amending the date of your transactions. You can edit it after matching, adding, or categorising the transaction.
To do so, you can open the transaction, then edit the date. Before doing so, I recommend double-checking the correct date as this might cause discrepancies between your bank statement and QuickBooks records.
To learn more about reviewing your transactions, see this article for a guide: Categorise and match online bank transactions in QuickBooks Online.
Once you're ready to reconcile, check this resource for the workflow: Reconcile an account in QuickBooks Online.
Please know that I'm just a reply away if you need any further assistance in managing your transactions. Wishing you all the best.