i blocked this files

Requirements::block('jsparty/prototype.js');
Requirements::block('jsparty/behaviour.js');
Requirements::block("jsparty/scriptaculous.js");
Requirements::block("jsparty/loader.js");
Requirements::block('jsparty/prototype_improvements.js');
Requirements::block('sapphire/javascript/Validator.js');
Requirements::block('sapphire/javascript/lang/en_US.js');

but still have Behaviour.register({ for form

<script type="text/javascript">//<![CDATA[
Behaviour.register({
   "#Form_formularz_en": {
      validateDate: function(fieldName) {
         var el = _CURRENT_FORM.elements[fieldName];
         var value = $F(el);
         
         if(value && value.length > 0 && !value.match(/^[0-9]{1,2}\/[0-9]{1,2}\/[0-90-9]{2,4}$/)) {
            validationError(el,"Please enter a valid date format (DD/MM/YYYY).","validation",false);
            return false;
         }
         return true;
      }
   }
});

I'm using 2.4 and I've added

you could also remove the validation:

http://doc.silverstripe.org/Validator

Also look at the following Docuemnt