So, It's not the first time I ask that kind of question but it's still not working...
I've put a date picker like this :
<script>
    $(document).ready(function () {
        $('.date').datepicker({ dateFormat: "dd/mm/yy", firstDay: 1 });
    });
</script>
And I call it this way :
@Html.TextBox("date", null, new { @class = "date", @Value = DateTime.Today.Date })
The problem is : as you see I'd like to have a dd/mm/yy format and that's the case when I select a date, it's in dd/mm/yy but when I push the submit button, it's not going to the controller and the datepicker shows up like to say : "Hey you made a mistake, I want a mm/dd/yy format"...
I've tried to remove the client side validation with @{ Html.EnableClientValidation(false); } but it doesn't change anything.... 
Can please someone help me ? Thanks in advance !
EDIT : Like I said, maybe not clearly enought, the problem is not coming from the server but from the client ! I have disable client validation in my web.config and it's now working