Hello Lee W,
I can see that you've tried a few ways to try and change the date format within your QuickBooks Desktop account to no avail. I want you to get the support you deserve in order to get to the bottom of this as soon as possible. as my colleague stated earlier in this thread, I recommend contacting our support team outside the Community, as they'll be able to do try some more steps with you to get the date format changed. You can find the different methods to reach out to them within the QuickBooks Desktop Software Support Policies.
if you have any more questions about QuickBooks Desktop, feel free to ask them here.
