How to define date formats in a Drupal modules as a features export is only exporting half of the information.

define_date_formats_in_code.php

<?php
/**
 * Implements hook_date_formats().
 *
 */
function my_module_date_formats() {
  return array(
    array(
      'type' => 'my_module_year_only',
      'format' => 'Y',
      
      // This format is used for german and english. 
      // You need to separate this in most real life cases.
      // The same format for two languages makes sense if to countries use the same format.
      // e.g.: Austria and Germany; or Germany and Swiss
      'locales' => array('de', 'en'),  
    ),
    array(
      'type' => 'my_module_short',
      'format' => 'd.m.Y',
      'locales' => array('de', 'en'),
    ),
    array(
      'type' => 'my_module_medium',
      'format' => 'D, d.m.Y',
      'locales' => array('de', 'en'),
    ),
    array(
      'type' => 'my_module_month_only_long',
      'format' => 'F',
      'locales' => array('de', 'en'),
    ),
  );

}

/**
 * Implements hook_date_format_types().
 *
 * Setting up some additional date types.
 */
function my_module_date_format_types() {
  // Define the date format types.
  return array(
    'my_module_year_only' => t('My Module year only'),
    'my_module_short' => t('My Module short'),
    'my_module_medium' => t('My Module medium'),
    'my_module_month_only_long' => t('My Module month only long'),
  );
}