tokens

<?php
/**
 * @file
 * Provides a token for building URL aliases for NGO articles.
 */

/**
 * Implements hook_token_info().
 */
function example_token_token_info() {
  $info['tokens']['node']['example-category'] = array(
    'name' => t('New Date Format'),
    'description' => t('Date field value, formatted nicely'),
  );
  return $info;
}

/**
 * Implements hook_tokens().
 */
function example_token_tokens($type, $tokens, array $data = array(), array $options = array()) {
  $replacements = array();

  if ($type == 'node' && !empty($data['node'])) {
    $node = $data['node'];

    foreach ($tokens as $name => $original) {
      switch ($name) {
        // Simple key values on the node.
        case 'example-category':
          $lang = $node->language;
          $replace = array();
          if (!empty($node->field_date[$lang])) {
            $date = $node->field_date[$lang][0]['value'];
            $replacements[$original] = format_date($date, 'custom', 'y-m-d');
          }

          break;
      }
    }
  }

  return $replacements;
}