public static Date::processDate(&$element, FormStateInterface $form_state, &$complete_form)
Processes a date form element.
Parameters
array $element: The form element to process. Properties used:
#attributes: An associative array containing:
type: The type of date field rendered.
#date_date_format: The date format used in PHP formats.
\Drupal\Core\Form\FormStateInterface $form_state: The current state of the form.
array $complete_form: The complete form structure.
Return value
a