diff --git a/phpBB/includes/cron.php b/phpBB/includes/cron.php
deleted file mode 100644
index b9a1bb778a..0000000000
--- a/phpBB/includes/cron.php
+++ /dev/null
@@ -1,164 +0,0 @@
-<?php
-/**
-*
-* @package phpBB3
-* @version $Id$
-* @copyright (c) 2010 phpBB Group
-* @license http://opensource.org/licenses/gpl-license.php GNU Public License
-*
-*/
-
-/**
-* @ignore
-*/
-if (!defined('IN_PHPBB'))
-{
-	exit;
-}
-
-/**
-* Cron class
-* @package phpBB3
-*/
-class cron
-{
-	var $tasks = array();
-
-	function cron()
-	{
-		global $config, $phpbb_root_path, $phpEx;
-		$modules = $config['cron_modules'];
-		$modules = explode(',', $modules);
-		foreach ($modules as $module)
-		{
-			// explode will return array("") when exploding an empty string;
-			// users may also specify something like foo,,bar.
-			// Account for module being possibly empty
-			if (!empty($module))
-			{
-				// Misspelling or specifying nonexistent modules here may make the board
-				// unusable due to error messages screwing up header output
-				include_once($phpbb_root_path . "includes/cron/$module.$phpEx");
-				$cron_class = "cron_tasks_$module";
-				$object = new $cron_class;
-				foreach ($object->tasks as $cron_type => $params)
-				{
-					$params['object'] = $object;
-					$this->tasks[$cron_type] = $params;
-				}
-			}
-		}
-	}
-
-	function is_valid_task($cron_type)
-	{
-		return isset($this->tasks[$cron_type]);
-	}
-
-	function is_task_runnable($cron_type, $args=null)
-	{
-		global $config;
-		$time_now = time();
-		$cron_params = $this->tasks[$cron_type];
-		if ($cron_params['enable_config'] && !$config[$cron_params['enable_config']])
-		{
-			return false;
-		}
-		if ($cron_param['custom_condition'])
-		{
-			$callable = array($cron_params['object'], $cron_type . '_condition');
-			if ($args)
-			{
-				$answer = call_user_func_array($callable, $args);
-			} else
-			{
-				$answer = call_user_func($callable);
-			}
-			if (!$answer)
-			{
-				return false;
-			}
-		}
-		if ($time_now - $config[$cron_params['interval_config']] > $config[$cron_params['last_run_config']])
-		{
-			return true;
-		}
-		return false;
-	}
-
-	function is_task_shutdown_function_compatible($cron_type)
-	{
-		$cron_params = $this->tasks[$cron_type];
-		if (isset($cron_params['shutdown_function_condition']))
-		{
-			return call_user_func(array($cron_params->object, $cron_type . '_shutdown_function_condition'));
-		} else
-		{
-			return true;
-		}
-	}
-
-	function determine_cron_mode_param()
-	{
-		global $config;
-		if ($config['use_system_cron'])
-		{
-			$mode = 'run_from_system';
-		} else
-		{
-			$mode_param = 'run_from_phpbb';
-		}
-		return $mode_param;
-	}
-
-	function find_one_runnable_task()
-	{
-		$mode_param = $this->determine_cron_mode_param();
-		foreach ($this->tasks as $cron_type => $cron_params)
-		{
-			if ($cron_params[$mode_param] && $this->is_task_runnable($cron_type))
-			{
-				return $cron_type;
-			}
-		}
-		return null;
-	}
-
-	function find_all_runnable_tasks()
-	{
-		$mode_param = $this->determine_cron_mode_param();
-		$tasks = array();
-		foreach ($this->tasks as $cron_type => $cron_params)
-		{
-			if ($cron_params[$mode_param] && $this->is_task_runnable($cron_type))
-			{
-				$tasks[] = $cron_type;
-			}
-		}
-		return $tasks;
-	}
-
-	function generate_task_code($cron_type, $args=array())
-	{
-		$cron_params = $this->tasks[$cron_type];
-		if ($cron_params['custom_code'])
-		{
-			$code = call_user_func_array(array($cron_params['object'], $cron_type . '_code'), $args);
-		} else
-		{
-			$code = $this->generate_generic_task_code($cron_type);
-		}
-		return $code;
-	}
-
-	function generate_generic_task_code($cron_type)
-	{
-		global $phpbb_root_path, $phpEx;
-		return '<img src="' . append_sid($phpbb_root_path . 'cron.' . $phpEx, 'cron_type=' . $cron_type) . '" width="1" height="1" alt="cron" />';
-	}
-
-	function run_task($cron_type)
-	{
-		call_user_func(array($this->tasks[$cron_type]['object'], 'run_' . $cron_type));
-	}
-}
diff --git a/phpBB/includes/cron_lock.php b/phpBB/includes/cron/cron_lock.php
similarity index 100%
rename from phpBB/includes/cron_lock.php
rename to phpBB/includes/cron/cron_lock.php
diff --git a/phpBB/includes/cron/cron_manager.php b/phpBB/includes/cron/cron_manager.php
new file mode 100644
index 0000000000..5ee06ac102
--- /dev/null
+++ b/phpBB/includes/cron/cron_manager.php
@@ -0,0 +1,175 @@
+<?php
+/**
+*
+* @package phpBB3
+* @version $Id$
+* @copyright (c) 2010 phpBB Group
+* @license http://opensource.org/licenses/gpl-license.php GNU Public License
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+/**
+* Cron manager class.
+*
+* Finds installed cron tasks, stores task objects, provides task selection.
+*
+* @package phpBB3
+*/
+class cron_manager
+{
+	private $tasks = array();
+
+	public function __construct()
+	{
+		$task_files = $this->find_cron_task_files();
+		$this->load_tasks($task_files);
+	}
+
+	/**
+	* Finds cron task files.
+	*
+	* A cron task file must follow the naming convention:
+	* includes/cron/tasks/$mod/$name.php.
+	* $mod is core for tasks that are part of phpbb.
+	* Modifications should use their name as $mod.
+	* $name is the name of the cron task.
+	* Cron task is expected to be a class named cron_task_${mod}_${name}.
+	*
+	* Todo: consider caching found task file list in global cache.
+	*/
+	public function find_cron_task_files()
+	{
+		global $phpbb_root_path, $phpEx;
+
+		$tasks_root_path = $phpbb_root_path . 'includes/cron/tasks';
+		$dir = opendir($tasks_root_path);
+		$task_dirs = array();
+		while (($entry = readdir($dir)) !== false)
+		{
+			// ignore ., .. and dot directories
+			// todo: change is_dir to account for symlinks
+			if ($entry[0] == '.' || !is_dir($entry))
+			{
+				continue;
+			}
+			$task_dirs[] = $entry;
+		}
+		closedir($dir);
+
+		$ext = '.' . $phpEx;
+		$ext_length = strlen($ext);
+		$task_files = array();
+		foreach ($task_dirs as $task_dir)
+		{
+			$path = $phpbb_root_path . 'includes/cron/tasks/' . $task_dir;
+			$dir = opendir($path);
+			while (($entry = readdir($dir)) !== false && substr($entry, -$ext_length) == $ext)
+			{
+				$task_file = substr($entry, 0, -$ext_length);
+				$task_files[] = array($task_dir, $task_file);
+			}
+			closedir($dir);
+		}
+		return $task_files;
+	}
+
+	/**
+	* Checks whether $name is a valid identifier, and therefore part of valid cron task class name.
+	*/
+	public function is_valid_name($name)
+	{
+		return preg_match('/^[a-zA-Z][a-zA-Z0-9_]*$/', $name);
+	}
+
+	public function load_tasks($task_files)
+	{
+		global $phpbb_root_path, $phpEx;
+
+		foreach ($task_files as $task_file)
+		{
+			list($mod, $filename) = $task_file;
+			if ($this->is_valid_name($mod) && $this->is_valid_name($filename))
+			{
+				include_once($phpbb_root_path . "includes/cron/$mod/$filename.$phpEx");
+				$class = "cron_task_${mod}_${filename}";
+				$object = new $class;
+				$this->tasks[] = $object;
+			}
+		}
+	}
+
+	/**
+	* Finds a task that is ready to run.
+	*
+	* If several tasks are ready, any one of them could be returned.
+	*/
+	function find_one_ready_task()
+	{
+		foreach ($this->tasks as $task)
+		{
+			if ($task->is_ready())
+			{
+				return $task;
+			}
+		}
+		return null;
+	}
+
+	/**
+	* Finds all tasks that are ready to run.
+	*/
+	function find_all_ready_tasks()
+	{
+		$tasks = array();
+		foreach ($this->tasks as $task)
+		{
+			if ($task->is_ready())
+			{
+				$tasks[] = $task;
+			}
+		}
+		return $tasks;
+	}
+
+	/**
+	* Finds a task by name.
+	*
+	* Web runner uses this method to resolve names to tasks.
+	*/
+	function find_task($name)
+	{
+		foreach ($this->tasks as $task)
+		{
+			if ($task->get_name() == $name)
+			{
+				return $task;
+			}
+		}
+		return null;
+	}
+
+	function instantiate_task($name, $args)
+	{
+		$task = $this->find_task($name);
+		if ($task)
+		{
+			$class = get_class($task);
+			$task = new $class($args);
+		}
+		return $task;
+	}
+
+	function generate_generic_task_code($cron_type)
+	{
+		global $phpbb_root_path, $phpEx;
+		return '<img src="' . $url . '" width="1" height="1" alt="cron" />';
+	}
+}
diff --git a/phpBB/includes/cron_task.php b/phpBB/includes/cron/cron_task.php
similarity index 100%
rename from phpBB/includes/cron_task.php
rename to phpBB/includes/cron/cron_task.php
diff --git a/phpBB/includes/cron_task_base.php b/phpBB/includes/cron/cron_task_base.php
similarity index 100%
rename from phpBB/includes/cron_task_base.php
rename to phpBB/includes/cron/cron_task_base.php
diff --git a/phpBB/includes/cron/cron_task_wrapper.php b/phpBB/includes/cron/cron_task_wrapper.php
new file mode 100644
index 0000000000..3919e4f049
--- /dev/null
+++ b/phpBB/includes/cron/cron_task_wrapper.php
@@ -0,0 +1,68 @@
+<?php
+/**
+*
+* @package phpBB3
+* @version $Id$
+* @copyright (c) 2010 phpBB Group
+* @license http://opensource.org/licenses/gpl-license.php GNU Public License
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+/**
+* Cron task wrapper class.
+* Enhances cron tasks with convenience methods that work identically for all tasks.
+*
+* @package phpBB3
+*/
+class cron_task_wrapper
+{
+	public function __construct($task)
+	{
+		$this->task = $task;
+	}
+
+	/**
+	* Returns whether the wrapped task is ready to run.
+	*
+	* A task is ready to run when it is runnable according to current configuration
+	* and enough time has passed since it was last run.
+	*/
+	public function is_ready()
+	{
+		return $this->task->is_runnable() && $this->task->should_run();
+	}
+
+	/**
+	* Returns the name of wrapped task.
+	*/
+	public function get_name()
+	{
+		$class = get_class($this->task);
+		return preg_replace('/^cron_task_/', '', $class);
+	}
+
+	public function get_url()
+	{
+		global $phpbb_root_path, $phpEx;
+
+		$name = $this->get_name();
+		$url = append_sid($phpbb_root_path . 'cron.' . $phpEx, 'cron_type=' . $name);
+		return $url;
+	}
+
+	/**
+	* Forwards all other method calls to the wrapped task implementation.
+	*/
+	public function __call($name, $args)
+	{
+		return call_user_func_array(array($this->task, $name), $args);
+	}
+}
diff --git a/phpBB/includes/cron/standard.php b/phpBB/includes/cron/standard.php
deleted file mode 100644
index 1cb8738f17..0000000000
--- a/phpBB/includes/cron/standard.php
+++ /dev/null
@@ -1,163 +0,0 @@
-<?php
-/**
-*
-* @package phpBB3
-* @version $Id$
-* @copyright (c) 2010 phpBB Group
-* @license http://opensource.org/licenses/gpl-license.php GNU Public License
-*
-*/
-
-/**
-* @ignore
-*/
-if (!defined('IN_PHPBB'))
-{
-	exit;
-}
-
-/**
-* Standard cron tasks
-* @package phpBB3
-*/
-class cron_tasks_standard
-{
-	var $tasks = array(
-		// key: cron type
-		// values: config name for enable/disable flag,
-		//         whether to check condition function to determine if the task can/should be run,
-		//         config name for interval,
-		//         config name for last run time,
-		//         whether task should be considered in phpbb cron mode,
-		//         whether task should be considered in system cron mode,
-		//         whether task requires special code generation
-		'prune_all_forums' => array(
-			'custom_condition' => true,
-			'run_from_system' => true,
-		),
-		'prune_forum' => array(
-			'custom_condition' => true,
-			'custom_code' => true,
-		),
-		'queue' => array(
-			'custom_condition' => true,
-			'interval_config' => 'queue_interval_config',
-			'last_run_config' => 'last_queue_run',
-			'run_from_phpbb' => true,
-			'run_from_system' => true,
-			'shutdown_function_condition' => true,
-		),
-		'tidy_cache' => array(
-			'custom_condition' => true,
-			'interval_config' => 'cache_gc',
-			'last_run_config' => 'cache_last_gc',
-			'run_from_phpbb' => true,
-			'run_from_system' => true,
-		),
-		'tidy_database' => array(
-			'interval_config' => 'database_gc',
-			'last_run_config' => 'database_last_gc',
-			'run_from_phpbb' => true,
-			'run_from_system' => true,
-		),
-		'tidy_search' => array(
-			'interval_config' => 'search_gc',
-			'last_run_config' => 'search_last_gc',
-			'run_from_phpbb' => true,
-			'run_from_system' => true,
-		),
-		'tidy_sessions' => array(
-			'interval_config' => 'session_gc',
-			'last_run_config' => 'session_last_gc',
-			'run_from_phpbb' => true,
-			'run_from_system' => true,
-		),
-		'tidy_warnings' => array(
-			'enable_config' => 'warnings_expire_days',
-			'interval_config' => 'warnings_gc',
-			'last_run_config' => 'warnings_last_gc',
-			'run_from_phpbb' => true,
-			'run_from_system' => true,
-		),
-	);
-	
-	function prune_forum_condition($forum_data) {
-		return $forum_data['enable_prune'] && $forum_data['prune_next'] < time();
-	}
-	
-	function prune_forum_code($forum_id) {
-		global $phpbb_root_path, $phpEx;
-		return '<img src="' . append_sid($phpbb_root_path . 'cron.' . $phpEx, 'cron_type=prune_forum&amp;f=' . $forum_id) . '" alt="cron" width="1" height="1" />';
-	}
-	
-	function run_prune_forum() {
-	}
-	
-	function queue_condition() {
-		global $phpbb_root_path, $phpEx;
-		return file_exists($phpbb_root_path . 'cache/queue.' . $phpEx);
-	}
-	
-	function queue_shutdown_function_condition() {
-		global $config;
-		return !$config['smtp_delivery'];
-	}
-	
-	function run_queue() {
-		global $phpbb_root_path, $phpEx;
-		include_once($phpbb_root_path . 'includes/functions_messenger.' . $phpEx);
-		$queue = new queue();
-		$queue->process();
-	}
-	
-	function tidy_cache_condition() {
-		global $cache;
-		return method_exists($cache, 'tidy');
-	}
-	
-	function run_tidy_cache() {
-		global $cache;
-		$cache->tidy();
-	}
-	
-	function run_tidy_database() {
-		include_once($phpbb_root_path . 'includes/functions_admin.' . $phpEx);
-		tidy_database();
-	}
-	
-	function tidy_search_condition() {
-		global $phpbb_root_path, $phpEx, $config;
-		
-		// Select the search method
-		$search_type = basename($config['search_type']);
-		
-		return file_exists($phpbb_root_path . 'includes/search/' . $search_type . '.' . $phpEx);
-	}
-	
-	function run_tidy_search() {
-		global $phpbb_root_path, $phpEx, $config, $error;
-		
-		// Select the search method
-		$search_type = basename($config['search_type']);
-		
-		include_once("{$phpbb_root_path}includes/search/$search_type.$phpEx");
-
-		// We do some additional checks in the module to ensure it can actually be utilised
-		$error = false;
-		$search = new $search_type($error);
-		
-		if (!$error) {
-			$search->tidy();
-		}
-	}
-	
-	function run_tidy_sessions() {
-		global $user;
-		$user->session_gc();
-	}
-	
-	function run_tidy_warnings() {
-		include_once($phpbb_root_path . 'includes/functions_admin.' . $phpEx);
-		tidy_warnings();
-	}
-}
diff --git a/phpBB/includes/cron_tasks/standard/prune_all_forums.php b/phpBB/includes/cron/tasks/core/prune_all_forums.php
similarity index 95%
rename from phpBB/includes/cron_tasks/standard/prune_all_forums.php
rename to phpBB/includes/cron/tasks/core/prune_all_forums.php
index 569752dcb0..13286de2b0 100644
--- a/phpBB/includes/cron_tasks/standard/prune_all_forums.php
+++ b/phpBB/includes/cron/tasks/core/prune_all_forums.php
@@ -25,7 +25,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class prune_all_forums_cron_task extends cron_task_base
+class cron_task_core_prune_all_forums extends cron_task_base
 {
 	/**
 	* Runs this cron task.
diff --git a/phpBB/includes/cron_tasks/standard/prune_forum.php b/phpBB/includes/cron/tasks/core/prune_forum.php
similarity index 96%
rename from phpBB/includes/cron_tasks/standard/prune_forum.php
rename to phpBB/includes/cron/tasks/core/prune_forum.php
index f4ef2ea6dd..4925447162 100644
--- a/phpBB/includes/cron_tasks/standard/prune_forum.php
+++ b/phpBB/includes/cron/tasks/core/prune_forum.php
@@ -25,7 +25,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class prune_forum_cron_task extends cron_task_base implements parametrized_cron_task
+class cron_task_core_prune_forum extends cron_task_base implements parametrized_cron_task
 {
 	/**
 	* Constructor.
diff --git a/phpBB/includes/cron_tasks/standard/queue.php b/phpBB/includes/cron/tasks/core/queue.php
similarity index 96%
rename from phpBB/includes/cron_tasks/standard/queue.php
rename to phpBB/includes/cron/tasks/core/queue.php
index 6a69799ef4..d7dfeb9319 100644
--- a/phpBB/includes/cron_tasks/standard/queue.php
+++ b/phpBB/includes/cron/tasks/core/queue.php
@@ -21,7 +21,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class queue_cron_task extends cron_task_base
+class cron_task_core_queue extends cron_task_base
 {
 	/**
 	* Runs this cron task.
diff --git a/phpBB/includes/cron_tasks/standard/tidy_cache.php b/phpBB/includes/cron/tasks/core/tidy_cache.php
similarity index 93%
rename from phpBB/includes/cron_tasks/standard/tidy_cache.php
rename to phpBB/includes/cron/tasks/core/tidy_cache.php
index 7c47be06c1..69038a8a5a 100644
--- a/phpBB/includes/cron_tasks/standard/tidy_cache.php
+++ b/phpBB/includes/cron/tasks/core/tidy_cache.php
@@ -21,7 +21,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class tidy_cache_cron_task extends cron_task_base
+class cron_task_core_tidy_cache extends cron_task_base
 {
 	/**
 	* Runs this cron task.
diff --git a/phpBB/includes/cron_tasks/standard/tidy_database.php b/phpBB/includes/cron/tasks/core/tidy_database.php
similarity index 92%
rename from phpBB/includes/cron_tasks/standard/tidy_database.php
rename to phpBB/includes/cron/tasks/core/tidy_database.php
index 16a17b3538..c6c2a60445 100644
--- a/phpBB/includes/cron_tasks/standard/tidy_database.php
+++ b/phpBB/includes/cron/tasks/core/tidy_database.php
@@ -21,7 +21,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class tidy_database_cron_task extends cron_task_base
+class cron_task_core_tidy_database extends cron_task_base
 {
 	/**
 	* Runs this cron task.
diff --git a/phpBB/includes/cron_tasks/standard/tidy_search.php b/phpBB/includes/cron/tasks/core/tidy_search.php
similarity index 96%
rename from phpBB/includes/cron_tasks/standard/tidy_search.php
rename to phpBB/includes/cron/tasks/core/tidy_search.php
index ac42c26689..0f409d114a 100644
--- a/phpBB/includes/cron_tasks/standard/tidy_search.php
+++ b/phpBB/includes/cron/tasks/core/tidy_search.php
@@ -23,7 +23,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class tidy_sessions_cron_task extends cron_task_base
+class cron_task_core_tidy_sessions extends cron_task_base
 {
 	/**
 	* Runs this cron task.
diff --git a/phpBB/includes/cron_tasks/standard/tidy_sessions.php b/phpBB/includes/cron/tasks/core/tidy_sessions.php
similarity index 91%
rename from phpBB/includes/cron_tasks/standard/tidy_sessions.php
rename to phpBB/includes/cron/tasks/core/tidy_sessions.php
index 6ff2dee14b..ea6aa70699 100644
--- a/phpBB/includes/cron_tasks/standard/tidy_sessions.php
+++ b/phpBB/includes/cron/tasks/core/tidy_sessions.php
@@ -21,7 +21,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class tidy_sessions_cron_task extends cron_task_base
+class cron_task_core_tidy_sessions extends cron_task_base
 {
 	/**
 	* Runs this cron task.
diff --git a/phpBB/includes/cron_tasks/standard/tidy_warnings.php b/phpBB/includes/cron/tasks/core/tidy_warnings.php
similarity index 94%
rename from phpBB/includes/cron_tasks/standard/tidy_warnings.php
rename to phpBB/includes/cron/tasks/core/tidy_warnings.php
index 059125b18d..c1ab14d788 100644
--- a/phpBB/includes/cron_tasks/standard/tidy_warnings.php
+++ b/phpBB/includes/cron/tasks/core/tidy_warnings.php
@@ -23,7 +23,7 @@ if (!defined('IN_PHPBB'))
 *
 * @package phpBB3
 */
-class tidy_warnings_cron_task extends cron_task_base
+class cron_task_core_tidy_warnings extends cron_task_base
 {
 	/**
 	* Runs this cron task.
diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index eb787bfc62..418e8dc51d 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -4617,11 +4617,12 @@ function page_footer($run_cron = true)
 	if ($call_cron)
 	{
 		global $cron;
-		$cron_type = $cron->find_one_runnable_task();
+		$task = $cron->find_one_ready_task();
 
-		if ($cron_type)
+		if ($task)
 		{
-			$template->assign_var('RUN_CRON_TASK', $cron->generate_task_code($cron_type));
+			$url = $task->get_url();
+			$template->assign_var('RUN_CRON_TASK', '<img src="' . $url . '" width="1" height="1" alt="cron" />');
 		}
 	}
 
diff --git a/phpBB/viewforum.php b/phpBB/viewforum.php
index 8a06e28394..a3fd9fa6fb 100644
--- a/phpBB/viewforum.php
+++ b/phpBB/viewforum.php
@@ -193,9 +193,13 @@ if ($forum_data['forum_topics_per_page'])
 }
 
 // Do the forum Prune thang - cron type job ...
-if (!$config['use_system_cron'] && $cron->is_task_runnable('prune_forum', array($forum_data)))
+if (!$config['use_system_cron'])
 {
-	$template->assign_var('RUN_CRON_TASK', $cron->generate_task_code('prune_forum', array($forum_id)));
+	$task = $cron->instantiate_task('core_prune_forum', $forum_data);
+	if ($task && $task->is_ready()) {
+		$url = $task->get_url();
+		$template->assign_var('RUN_CRON_TASK', '<img src="' . $url . '" width="1" height="1" alt="cron" />');
+	}
 }
 
 // Forum rules and subscription info