I ended up using a date picker instead of the by default date form input from squarespace.
If any one is interested:
HTML forms have a type of input called date that come by default with a date picker, you can't change the type with squarespace but you can override it. Not all the old version of browsers will support this form input - link
Create a normal txt input on your form
copy the id of the input field (through right click -> inspect)
open the settings of the page then advanced
paste the follow code and replace YOUR-ID with the ID you copied
<script src="https://code.jquery.com/jquery-3.6.1.min.js" integrity="sha256-o88AwQnZB+VDvE9tvIXrMQaPlFFSUTR+nldQm1LuPXQ=" crossorigin="anonymous"></script>
<script>
$( document ).ready(function() {
$('#YOUR-ID').attr("type", "date");
$('.field-element[id^="number"]').attr("type", "number");
});
</script>
Also added a replacement of all the txt fields that should be number into number fields
A shame that Squarespace doesn't use the correct type for their forms, number should be input type="number" instead of type="text"...