diff --git a/core/modules/locale/locale.batch.inc b/core/modules/locale/locale.batch.inc
new file mode 100644
index 0000000..93a85aa
--- /dev/null
+++ b/core/modules/locale/locale.batch.inc
@@ -0,0 +1,181 @@
+<?php
+
+/**
+ * @file
+ *   @todo
+ */
+
+/**
+ * Build a batch to get the status of remote and local translation files.
+ *
+ * The batch process fetches the state of both remote and (if configured) local
+ * translation files. The data of the most recent translation is stored per
+ * per project and per language. This data is stored a state variable
+ * 'locale_translation_status'. The timestamp it was last updated is stored
+ * in the state variable 'locale_translation_status_last_update'.
+ *
+ * @param array $sources
+ *   Array of translation source objects for which to check the state of
+ *   translation source files.
+ */
+function locale_translation_batch_status_build($sources) {
+  $operations = array();
+
+  // Set the batch processes for remote sources.
+  foreach ($sources as $source) {
+    $operations[] = array('locale_translation_batch_status_fetch_remote', array($source));
+  }
+
+  // Only fetch local data if it's configured to do so.
+  // @todo We should make an exception for modules without remote source.
+  //       But this requires a flag per project to be set when the .info data is parsed.
+  $check_local = variable_get('locale_translation_check_mode', LOCALE_TRANSLATION_CHECK_ALL) & LOCALE_TRANSLATION_CHECK_LOCAL;
+  if ($check_local) {
+    $operations[] = array('locale_translation_batch_status_fetch_local', array($sources));
+  }
+
+  // Compare results of local and remote and store the most recent.
+  $operations[] = array('locale_translation_batch_status_compare', array());
+
+  $batch = array(
+    'operations' => $operations,
+    'title' => t('Checking available translations'),
+    'finished' => 'locale_translation_batch_status_finished',
+    'error_message' => t('Error checking available translation updates.'),
+    'file' => drupal_get_path('module', 'locale') . '/locale.batch.inc',
+  );
+  return $batch;
+}
+
+/**
+ * Batch operation callback: Check the availability of a remote po file.
+ *
+ * Checks the presence and creation time of one po file per batch process. The
+ * file URL and timestamp are stored.
+ *
+ * @param array $source
+ *   A translation source object of the project for which to check the state of
+ *   a remote po file.
+ * @param array $context
+ *   The batch context array. The collected state is stored in the 'results'
+ *   parameter of the context.
+*/
+function locale_translation_batch_status_fetch_remote($source, &$context) {
+  // Check the translation file at the remote server and update the source
+  // data with the remote status.
+  $result = locale_translation_http_check($source->url);
+  if ($result && !empty($result->updated)) {
+
+    // Modify the source object with the result data.
+    // There may have been redirects so we store the resulting url.
+    $source->type = 'remote';
+    $source->fileurl = isset($result->redirect_url) ? $result->redirect_url : $source->url;
+    unset($source->url);
+    $source->timestamp = $result->updated;
+  }
+
+  // Store the source data in the context for later processing.
+  $context['results'][$source->name][$source->language]['remote'] = $source;
+}
+
+/**
+ * Batch operation callback: Check the availability of local po files.
+ *
+ * Checks the presence and creation time of po files in the local file system.
+ * The file path and the timestamp are stored.
+ *
+ * @param array $sources
+ *   Array of translation source objects of projects for which to check the
+ *   state of local po files.
+ * @param array $context
+ *   The batch context array. The collected state is stored in the 'results'
+ *   parameter of the context.
+ */
+function locale_translation_batch_status_fetch_local($sources, &$context) {
+  module_load_include('compare.inc', 'locale');
+
+  foreach ($sources as $source) {
+    // Get the status of local translation source and update the source data
+    // with this.
+    locale_translation_source_check_file($source);
+
+    // Store the source data in the context for later processing.
+    $context['results'][$source->name][$source->language]['local'] = $source;
+  }
+}
+
+/**
+ * Batch operation callback: Compare states and store the result.
+ *
+ * Compare the collected results of local and remote sources and store the most
+ * recent one. The collected result are stored in the 'results' element of the
+ * batch context parameter.
+ * The results are stored in the 'locale_translation_status' state. Other
+ * processes can collect this data once the batch is completed.
+ *
+ * @param array $context
+ *   The batch context array. The 'results' element contains a structured array
+ *   of project data with languages, local and remote source data.
+ */
+function locale_translation_batch_status_compare(&$context) {
+  module_load_include('compare.inc', 'locale');
+  $results = array();
+
+  foreach ($context['results'] as $project => $langcodes) {
+    foreach ($langcodes as $langcode => $sources) {
+      $local = $sources['local'] ? $sources['local']  : array();
+      $remote = $sources['remote'];
+      if ($result = _locale_translation_source_compare($local, $remote) < 0 ? $remote : $local) {
+        $results[$project][$langcode] = $result;
+      }
+    }
+  }
+
+  state()->set('locale_translation_status', $results);
+  state()->set('locale_translation_status_last_update', REQUEST_TIME);
+}
+
+/**
+ * Batch finished callback: Set result message.
+ *
+ * @param boolean $success
+ *   TRUE if batch succesfully completed.
+ * @param array $results
+ *   Batch results.
+ */
+function locale_translation_batch_status_finished($success, $results) {
+  $t = get_t();
+  if($success) {
+    if ($results) {
+      drupal_set_message(format_plural(
+        count($results),
+        'Checked available interface translation updates for one project.',
+        'Checked available interface translation updates for @count projects.'
+      ));
+    }
+  }
+  else {
+    drupal_set_message($t('An error occurred trying to check available interface translation updates.'), 'error');
+  }
+}
+
+/**
+ * Check if remote file exists and when it was last updated.
+ *
+ * @param string $url
+ *   URL of remote file.
+ * @param array $headers
+ *   HTTP request headers.
+ * @return stdClass
+ *   Result object containing the HTTP request headers, response code, headers,
+ *   data, redirect status and updated timestamp.
+ */
+// @todo Replace this with a stream wrapper? May use ReadOnlyStreamWrapper:
+//       http://drupal.org/node/1308054
+function locale_translation_http_check($url, $headers = array()) {
+  $result = drupal_http_request($url, array('headers' => $headers, 'method' => 'HEAD'));
+  if ($result && $result->code == '200') {
+    $result->updated = isset($result->headers['last-modified']) ? strtotime($result->headers['last-modified']) : 0;
+  }
+  return $result;
+}
diff --git a/core/modules/locale/locale.compare.inc b/core/modules/locale/locale.compare.inc
index 039eba3..d219055 100644
--- a/core/modules/locale/locale.compare.inc
+++ b/core/modules/locale/locale.compare.inc
@@ -12,6 +12,15 @@
  */
 const LOCALE_TRANSLATION_DEFAULT_SERVER_PATTERN = 'http://ftp.drupal.org/files/translations/%core/%project/%project-%version.%language.po';
 
+/**
+ * Threshold for timestamp comparison.
+ *
+ * Eliminates a difference between the download time and the actual .po file
+ * timestamp in seconds. The download time is stored in the database in
+ * {locale_file}.timestamp.
+ */
+const LOCALE_TRANSLATION_TIMESTAMP_THRESHOLD = 2;
+
 use Drupal\Core\Cache;
 
 /**
@@ -225,6 +234,10 @@ function _locale_translation_prepare_project_list($data, $type) {
     if (isset($file->info['interface translation project'])) {
       $data[$name]->info['project'] = $file->info['interface translation project'];
     }
+    // @todo Here we could mark projects which do not have a 'project' and therefore should not
+    //       be checked for a remote translation. Unless explictly provided by 'interface translation server'.
+    //       Use file_uri_scheme() here?
+
   }
   return $data;
 }
@@ -269,3 +282,220 @@ function locale_translation_build_server_pattern($project, $template) {
   );
   return strtr($template, $variables);
 }
+
+/**
+ * Check for the latest release of project translations.
+ *
+ * @param array $projects
+ *   Projects to check (objects).
+ * @param string $langcodes
+ *   Array of language codes to check for. Leave empty to check all languages.
+ *
+ * @return array
+ *   Available sources indexed by project and language.
+ */
+function locale_translation_check_projects($projects, $langcodes = NULL) {
+  module_load_include('batch.inc', 'locale');
+
+  $check_remote = variable_get('locale_translation_check_mode', LOCALE_TRANSLATION_CHECK_ALL) & LOCALE_TRANSLATION_CHECK_REMOTE;
+  if ($check_remote) {
+    // Retrieve the status of both remote and local translation sources by
+    // using a batch process.
+    locale_translation_check_projects_batch($projects, $langcodes);
+  }
+  else {
+    // Retrieve and save the status of local translations only.
+    locale_translation_check_projects_local($projects, $langcodes);
+  }
+}
+
+/**
+ * Gets and stores the status and creation timestamp of remote po files.
+ *
+ * A batch process is used to check for po files at remote locations and (if
+ * configured) to check for po file in the local file system. The most recent
+ * translation source states are stored in the state variable
+ * 'locale_translation_status'.
+ *
+ * @params array $projects
+ *   Array of translatable projects.
+ * @params array $langcodes
+ *   Array of language codes to check for. Leave empty to check all languages.
+ */
+function locale_translation_check_projects_batch($projects, $langcodes = NULL) {
+  $langcodes = $langcodes ? $langcodes : array_keys(locale_translatable_language_list());
+  $sources = array();
+  foreach ($projects as $name => $project) {
+    foreach ($langcodes as $langcode) {
+      $project_clone = clone $project;
+      $source = locale_translation_source_build($project_clone, $langcode);
+      $source->url = locale_translation_build_server_pattern($source, $source->server_pattern);
+      $sources[] = $source;
+    }
+  }
+
+  // Build and set the batch process.
+  module_load_include('batch.inc', 'locale');
+  $batch = locale_translation_batch_status_build($sources);
+  batch_set($batch);
+}
+
+/**
+ * Check and store the status and creation timestamp of local po files.
+ *
+ * Only po files in the local file system and checked. Any remote translation
+ * sources will be ignored. Results are stored in the state variable
+ * 'locale_translation_status'.
+ *
+ * Projects may contain a server_pattern option containing the pattern of the
+ * path to the po source files. If not defined the default translation directory
+ * is scanned for presence of po files. If defined the specified location is
+ * checked. The server_pattern can be set in the module's .info file or by
+ * using hook_locale_translation_projects_alter().
+ *
+ * The time/date the po file was written (PHP: filemtime()) is used as
+ * timestamp.
+ *
+ * @params array $projects
+ *   Array of translatable projects.
+ * @params array $langcodes
+ *   Array of language codes to check for. Leave empty to check all languages.
+ */
+function locale_translation_check_projects_local($projects, $langcodes = NULL) {
+  $langcodes = $langcodes ? $langcodes : array_keys(locale_translatable_language_list());
+  $results = array();
+
+  foreach ($projects as $name => $project) {
+    foreach ($langcodes as $langcode) {
+      $project_clone = clone $project;
+      $source = locale_translation_source_build($project_clone, $langcode);
+      if (locale_translation_source_check_file($source)) {
+        $results[$name][$langcode] = $source;
+      }
+    }
+  }
+
+  state()->set('locale_translation_status', $results);
+  state()->set('locale_translation_status_last_update', REQUEST_TIME);
+}
+
+/**
+ * Check whether a po file exists in the filesystem.
+ *
+ * It will search in the directory set in the translation source. Which defaults
+ * to the files/translations directory as set in the variable
+ * 'locale_translate_file_directory'.
+ *
+ * It will search for a file name as set in the translation source. Which
+ * defaults to LOCALE_TRANSLATION_DEFAULT_FILENAME. Per project this value
+ * can be overridden using the server_pattern directive in the module's .info
+ * file or by using hook_locale_translation_projects_alter().
+ *
+ * @param stdClass $source
+ *   Translation file object.
+ *   @see locale_translation_source_build()
+ *
+ * @return stdClass
+ *   File object (filename, basename, name) updated with data of the po file:
+ *   - "type": Fixed value 'local'.
+ *   - "uri": File name and path.
+ *   - "timestamp": Last updated time.
+ *   NULL if failure.
+ */
+// @todo incorporate translations:// streamwrapper. See http://drupal.org/node/1658842
+function locale_translation_source_check_file(&$source) {
+  $directory = $source->directory;
+  $filename = '/' . preg_quote($source->filename) . '$/';
+
+  // Get the time stamp and file date from file from the directory which matches
+  // the filename.
+  if ($files = drupal_system_listing($filename, $directory, 'name', 0)) {
+    $file = current($files);
+    $source->type = 'local';
+    $source->uri = $file->uri;
+    $source->timestamp = filemtime($file->uri);
+    return $file;
+  }
+  return NULL;
+}
+
+/**
+ * Build abstract translation source, to be mapped to a file or a download.
+ *
+ * @param stdClass $project
+ *   Project object.
+ * @param string $langcode
+ *   Language code.
+ * @param string $filename
+ *   File name of translation file. May contains placeholders.
+ *
+ * @return object
+ *   Source object, which may have these properties:
+ *   - "project": Project name.
+ *   - "language": Language code.
+ *   - "type": Source type 'remote' or 'local'.
+ *   - "uri": Local file path.
+ *   - "fileurl": Remote file URL for downloads.
+ *   - "directory": Directory of the local po file.
+ *   - "filename": File name.
+ *   - "keep": TRUE to keep the downloaded file. //@todo Is this still applicable?
+ *   - "timestamp": Last update time of the file.
+ */
+// @todo Move this file?
+function locale_translation_source_build($project, $langcode, $filename = LOCALE_TRANSLATION_DEFAULT_FILENAME) {
+  $source = clone $project;
+  $source->project = $project->name;
+  $source->language = $langcode;
+
+  // If the server_pattern contains a remote file path we check for a
+  // corresponding local po file in the local translation directory. If the server_pattern
+  // is a local po file path we chekc for a po file using this pattern.
+  module_load_include('inc', 'file');
+  if (file_uri_scheme($source->server_pattern)) {
+    $source->directory = variable_get('locale_translate_file_directory', conf_path() . '/files/translations');
+    $source->filename = locale_translation_build_server_pattern($source, $filename);
+  }
+  else {
+    $source->directory = dirname($source->server_pattern);
+    $source->filename = locale_translation_build_server_pattern($source, basename($source->server_pattern));
+  }
+
+  return $source;
+}
+
+/**
+ * Compare two update sources, looking for the newer one.
+ *
+ * The timestamp property of the source objects are used to determine which is
+ * the newer one.
+ *
+ * @param stdClass $source1
+ *   Source object of the first translation source.
+ * @param stdClass $source2
+ *   Source object of available update.
+ *
+ * @return integer
+ *   - "-1": $source1 < $source2 OR $source1 is missing.
+ *   - "0":  $source1 == $source2 OR both $source1 and $source2 are missing.
+ *   - "1":  $source1 > $source2 OR $source2 is missing.
+ */
+// @todo Move to locale.inc?
+function _locale_translation_source_compare($source1, $source2) {
+  if ($source1 && $source2) {
+    if (abs($source1->timestamp - $source2->timestamp) < LOCALE_TRANSLATION_TIMESTAMP_THRESHOLD) {
+      return 0;
+    }
+    else {
+      return $source1->timestamp > $source2->timestamp ? 1 : -1;
+    }
+  }
+  elseif ($source1 && !$source2) {
+    return 1;
+  }
+  elseif (!$source1 && $source2) {
+    return -1;
+  }
+  else {
+    return 0;
+  }
+}
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index a32d47d..34f645e 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -66,6 +66,43 @@ const LOCALE_NOT_CUSTOMIZED = 0;
  */
 const LOCALE_CUSTOMIZED = 1;
 
+/**
+ * Translation update mode: Use remote server only.
+ *
+ * When checking for available translation updates, only remote servers will be
+ * used. Any local translation file will be ignored. Custom modules and themes
+ * which have set a "server pattern" to use local translation files will still
+ * be checked.
+ */
+const LOCALE_TRANSLATION_CHECK_REMOTE = 1;
+
+/**
+ * Translation update mode: Use local files only.
+ *
+ * When checking for available translation updates, only local files will be
+ * used. Any local remote server will be ignored. Also custom modules and themes
+ * which have set a "server pattern" to use a remote translation server will be
+ * ignored.
+ */
+const LOCALE_TRANSLATION_CHECK_LOCAL = 2;
+
+/**
+ * Translation update mode: Use both remote and local files.
+ *
+ * When checking for available translation updates, both local and remote files
+ * will be checked.
+ */
+define('LOCALE_TRANSLATION_CHECK_ALL', LOCALE_TRANSLATION_CHECK_REMOTE | LOCALE_TRANSLATION_CHECK_LOCAL);
+
+/**
+ * Default file name of translation files stored in the local file system.
+ *
+ * The file name containing placeholders which are also used by the server
+ * pattern. See locale_translation_build_server_pattern() for supported placeholders.
+ */
+const LOCALE_TRANSLATION_DEFAULT_FILENAME = '%project-%version.%language.po';
+
+
 // ---------------------------------------------------------------------------------
 // Hook implementations
 
@@ -230,6 +267,26 @@ function locale_language_delete($language) {
   cache()->delete('locale:' . $language->langcode);
 }
 
+// ---------------------------------------------------------------------------------
+// Locale translation core functionality
+
+/**
+ * Returns list of translatable languages.
+ *
+ * @return array
+ *   Array of installed languages keyed by language name. English is omitted
+ *   unless its marked as translatable.
+ */
+function locale_translatable_language_list() {
+//drupal_static_reset('language_list');
+  $languages = language_list();
+//debug($languages);
+//debug(db_query('SELECT * FROM {language} ORDER BY weight ASC, name ASC')->fetchAllAssoc('langcode', PDO::FETCH_ASSOC));
+  if (!locale_translate_english()) {
+    unset($languages['en']);
+  }
+  return $languages;
+}
 
 // ---------------------------------------------------------------------------------
 // Locale core functionality
@@ -811,10 +868,7 @@ function _locale_invalidate_js($langcode = NULL) {
 
   if (empty($langcode)) {
     // Invalidate all languages.
-    $languages = language_list();
-    if (!locale_translate_english()) {
-      unset($languages['en']);
-    }
+    $languages = locale_translatable_language_list();
     foreach ($languages as $lcode => $data) {
       $parsed['refresh:' . $lcode] = 'waiting';
     }