<?php
use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Entity\EntityInterface;

/**
 * Implements hook_form_FORM_ID_alter().
 */
function myModule_form_views_exposed_form_alter(&$form, FormStateInterface $form_state, $form_id) {

  if (isset($form['#id']) && $form['#id'] == 'views-exposed-form-ContentType-DisplayId') {
    // If date filter set change if to select list of years.
    if (isset($form['field_date_value'])) {
      // Get options from cache.
      $options = &drupal_static(__FUNCTION__);
      if (is_null($options)) {
        // Set up cid.
        $cid = 'myModule:ContentType:year';
        // Get data from cache.
        $data = \Drupal::cache()->get($cid);
        if (!$data) {
          $options[''] = new TranslatableMarkup('Year');
          $query = \Drupal::entityQuery('node');
          $query->condition('type', 'ContentType')
            ->condition('status', 1)
            ->sort('field_date', 'ASC');
          $result = $query->execute();
          if ($result) {
            $nodes = Node::loadMultiple($result);
            foreach ($nodes as $key => $node) {
              if ($node->hasField('field_date')) {
                $date = $node->field_date->value;
                if ($date) {
                  $date = new DrupalDateTime($date, new DateTimeZone('UTC'));
                  $year = $date->format('Y');
                  if (!isset($options[$year])) {
                    $options['.*' . $year] = $year;
                  }
                }
              }
            }
          }
          // Cache tag.
          $cache_tags = ['node:ContentType:year'];
          // Set cache.
          \Drupal::cache()
            ->set($cid, $options, CacheBackendInterface::CACHE_PERMANENT, $cache_tags);
        }
        else {
          $options = $data->data;
        }
      }
      // Change the filter to select.
      $form['field_date_value'] = [
        '#type'          => 'select',
        '#options'       => $options,
        '#size'          => NULL,
        '#default_value' => '',
      ];
    }
  }
}

/**
 * Implements hook_ENTITY_TYPE_presave().
 */
function myModule_node_presave(EntityInterface $entity) {
  $bundle = $entity->bundle();
  if ($bundle == 'ContentType') {
    // Check if a ContentType updated has a new year, and invalidate the.
    // options cached used in the custom views filter for filtering by year.
    $cid = 'myModule:ContentType:year';
    $data = \Drupal::cache()->get($cid);
    if ($data) {
      if ($entity->hasField('field_date')) {
        $options = $data->data;
        $date = $entity->field_date->value;
        if ($date) {
          $date = new DrupalDateTime($date, new DateTimeZone('UTC'));
          $year = $date->format('Y');
          if (!isset($options['.*' . $year])) {
            Cache::invalidateTags(['node:ContentType:year']);
          }
        }
      }
    }
  }
}