Date.php

1. 9.x drupal/core/lib/Drupal/Core/TypedData/Type/Date.php
2. 9.x drupal/core/modules/views/lib/Drupal/views/Plugin/views/field/Date.php
3. 9.x drupal/core/modules/views/lib/Drupal/views/Plugin/views/argument/Date.php
4. 9.x drupal/core/modules/views/lib/Drupal/views/Plugin/views/sort/Date.php
5. 9.x drupal/core/modules/views/lib/Drupal/views/Plugin/views/filter/Date.php

<?php

/**
 * @file
 * Definition of Drupal\views\Plugin\views\sort\Date.
 */
namespace Drupal\views\Plugin\views\sort;

use Drupal\Core\Annotation\Plugin;

/**
 * Basic sort handler for dates.
 *
 * This handler enables granularity, which is the ability to make dates
 * equivalent based upon nearness.
 *
 * @Plugin(
 *   id = "date"
 * )
 */
class Date extends SortPluginBase {
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['granularity'] = array(
      'default' => 'second',
    );
    return $options;
  }
  public function buildOptionsForm(&$form, &$form_state) {
    parent::buildOptionsForm($form, $form_state);
    $form['granularity'] = array(
      '#type' => 'radios',
      '#title' => t('Granularity'),
      '#options' => array(
        'second' => t('Second'),
        'minute' => t('Minute'),
        'hour' => t('Hour'),
        'day' => t('Day'),
        'month' => t('Month'),
        'year' => t('Year'),
      ),
      '#description' => t('The granularity is the smallest unit to use when determining whether two dates are the same; for example, if the granularity is "Year" then all dates in 1999, regardless of when they fall in 1999, will be considered the same date.'),
      '#default_value' => $this->options['granularity'],
    );
  }

  /**
   * Called to add the sort to a query.
   */
  public function query() {
    $this
      ->ensureMyTable();
    switch ($this->options['granularity']) {
      case 'second':
      default:
        $this->query
          ->add_orderby($this->tableAlias, $this->realField, $this->options['order']);
        return;
      case 'minute':
        $formula = $this
          ->getSQLFormat('YmdHi');
        break;
      case 'hour':
        $formula = $this
          ->getSQLFormat('YmdH');
        break;
      case 'day':
        $formula = $this
          ->getSQLFormat('Ymd');
        break;
      case 'month':
        $formula = $this
          ->getSQLFormat('Ym');
        break;
      case 'year':
        $formula = $this
          ->getSQLFormat('Y');
        break;
    }

    // Add the field.
    $this->query
      ->add_orderby(NULL, $formula, $this->options['order'], $this->tableAlias . '_' . $this->field . '_' . $this->options['granularity']);
  }

}