Custom module for Drupal 7 defining a token for a custom field that stores its data in a `year` column (instead of `value`).

mymodule.module

<?php

declare(strict_types = 1);

/**
 * Implements hook_token_info().
 */
function mymodule_token_info() : array {
  $info['tokens']['node']['custom_year'] = array(
    'name' => t('Year Field Value'),
    'description' => t('Value from the year field.')
  );

  return $info;
}

/**
 * Implements hook_tokens().
 */
function mymodule_tokens($type, $tokens, array $data = array(), array $options = array()) : array {
  $replacements = [];

  if ($type == 'node' && !empty($data['node']) && array_key_exists('custom_year', $tokens)) {
    $replacements['[node:custom_year]'] = $data['node']->field_custom_year[LANGUAGE_NONE][0]['year'];
  }

  return $replacements;
}