You can change the day/month/year order for your reports and submission summaries. By default, the value is in the format YYYY-MM-DD.
You can change the format by doing the following;
This will only change the order for your own reports and submission results sent via email. If you want to change the display order of a date field on a form, click the Configure cog to the right of your date field, and select the desired format from the "Order of date" dropdown.