Somehow my invoice dates on most of my 2017 invoices have changed to Feb 2018 dates i am unable to change without a password what can i do?

Welcome to the Community, waylor.

It looks like you've already closed the books that's why you're unable to update the invoice date without a password. If you've forgotten it, let's go ahead and set a new one, so you can make changes to the transaction.I'll be happy to show you how:

1. First, sign in as an admin in QuickBooks Online.
2. Then, go to the Gear icon and choose Account and Settings.
3. Select the Advanced tab on the left.
4. Click the Accounting section.
5. Update and confirm the closing password.
6. Hit Save and Done.

Take a look at this article for more details: How to change the closing date password.

Once done, you can now update the invoice date. Here's how:

1. First, open the invoice and enter the correct transaction date.
2. Then, hit Save.
3. Enter the closing date password.
4. Lastly, click Yes.

If you need any help about the steps above, let me know and I'll be glad to assist. I hope to see you around more often.