Date field is sorted like text and not date in backend

Hi !
I have a date field named “checkin_date” set up like this :

{
“weekstart”: 1,
“format”: “DD-MM-YYYY” /* Europe format */
}
I use this field to sort bookings by their arrival
Unfortunately, when I want to sort my entries in the backend, it’s not sorted like date but more like text.

Sorted desc give me this :

30-04-2021
21-05-2021
14-05-2021
07-05-2021

But I need the dates to be sorted chronologically like this :

30-04-2021
07-05-2021
14-05-2021
21-05-2021

Is there a way to achieve this with the field options ? Did I missed something ?
Since it’s a date field I thought it would have been sorted like dates.
I’ve looked everywhere, did not found anything about it.

Thanks !