Smart Receipts inherits the date settings from your device's default.
First try to change this by:
1. Opening the settings app (on your phone itself).
2. Scrolling down to the "Date & time" section.
3. Changing the "Choose date format" option.
Note that some of the names might vary slightly based on your device itself (e.g. Samsung might put it slightly differently than HTC, but the core is the same).
If that doesn't work, though, note that recently Android became fully locale & language based (i.e. US English phones will have mm/DD/YYYY dates, whereas UK English phones will have DD/mm/YYYY dates). You may need to open the phone's language setting and try a different locale (e.g. move from English US to English UK).
We're planning to add an in-app setting to get away from this limitation of the system in the future. If you're still having problems, contact us at firstname.lastname@example.org and we'll walk you through the process in person.