Thanks for reaching out to the Community, chris-lindop2.
For now, the ability to change the date on reports in QuickBooks Online Mobile App for iPad is unavailable. You may consider using the browser on your iPad to access your QBO account. From there, you can generate and customise your report. Simply open the available web browser on your iPad, and then, type in qbo.intuit.com to enter your log in information.
- Go to the Reports menu.
- Select the Profit and Loss report.
- Adjust the date pf the report under the Report period section.
- Once done, click Run report.

To learn more information about customising report in QBO, please check it here.
Keep me posted if you need anything else.