I have used date field and selected Date only. There is calendar so I can select the exact date, but it requiretes different format. Please check attached picture.
Also following issue:
Warning: Undefined array key "object" in Drupal\Core\Datetime\Element\Datetime::validateDatetime() (line 371 of core\lib\Drupal\Core\Datetime\Element\Datetime.php).
Drupal\Core\Datetime\Element\Datetime::validateDatetime(Array, Object, Array)
call_user_func_array(Array, Array) (Line: 282)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object) (Line: 238)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object) (Line: 238)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object) (Line: 238)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object) (Line: 238)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object, 'node_nexus_wi_request_form') (Line: 118)
Drupal\Core\Form\FormValidator->validateForm('node_nexus_wi_request_form', Array, Object) (Line: 593)
Drupal\Core\Form\FormBuilder->processForm('node_nexus_wi_request_form', Array, Object) (Line: 325)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 169)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 718)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)Closed: outdated
1.0
Code
I have no idea about another date format. I guess your navigator use format d.m.Y, I don't have any other language to fix it. I tested on French Vietnamese English with chrome, firefox, edge browser. It post always Y-m-d format. I am basing this format to save to database.
Have you try another type date (timestamp)?