date-picker:
  js:
    script/site-datepicker.js : {}
  dependencies:
    - core/jquery
    - core/jquery.ui.datepicker

Drupal.behaviors.customDatepicker = {
  attach: function (context, settings) {
    jQuery(function () {
      jQuery("#datepicker").datepicker({
        dateFormat: "dd-mm-yy",
        altField: "input[data-drupal-selector=edit-created]",
        altFormat: "yy/mm/dd 23:59:59"
      });
    });
  }
};

{% if q is not empty %}
  {#
    This ensures that, if clean URLs are off, the 'q' is added first,
    as a hidden form element, so that it shows up first in the POST URL.
  #}
  {{ q }}
{% endif %}

<input id="datepicker" type="text">
<input data-drupal-selector="edit-created" data-msg-maxlength="This field field has a maximum length of 128." name="created" size="30" maxlength="128" aria-invalid="false" type="hidden">
{{ form|without('created') }}