Hi Sacha,
Welcome to the DocuSign Community!
We are glad to have you here and can't wait to help share as much knowledge as possible.
I am sorry to hear that you are getting a different date format that expected in your formula results, but I will clarify the topic for you.
It is expected behavior for formula outputs to default to US date format, unless a text box with a date format validation rule is called within the formula.
Taking this into consideration, you could add a blank text box with the required date format validation to work around this issue,
Feel free to let us know if you need further assistance with this.
Thank you for using DocuSign, we hope you have a wonderful rest of your day!