By the store do you mean on the Kobo website, or the Kobo devices?
From what I've seen on the website Kobo use US format but they spell out the month so it is not ambiguous. They use the correct date format for my country in email reciepts. Do you have a link to an example?
On the Kobo device you might be able to change a setting to display the date in your local format. For Kobo Touch/Glo/Mini see this thread:
https://www.mobileread.com/forums/sho...d.php?t=206200, it might be similar for Vox/Arc.