diff --git a/wp-includes/cron.php b/wp-includes/cron.php
index 65c5d8573a..50a95fde55 100644
--- a/wp-includes/cron.php
+++ b/wp-includes/cron.php
@@ -1,5 +1,24 @@
 <?php
+/**
+ * WordPress CRON API
+ *
+ * @package WordPress
+ */
 
+/**
+ * Schedules a hook to run only once.
+ *
+ * Schedules a hook which will be executed once by the Wordpress actions core at
+ * a time which you specify. The action will fire off when someone visits your
+ * WordPress site, if the schedule time has passed.
+ *
+ * @since 2.1.0
+ * @link http://codex.wordpress.org/Function_Reference/wp_schedule_single_event
+ *
+ * @param int $timestamp Timestamp for when to run the event.
+ * @param callback $hook Function or method to call, when cron is run.
+ * @param array $args Optional. Arguments to pass to the hook function.
+ */
 function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
 	$crons = _get_cron_array();
 	$key = md5(serialize($args));
@@ -8,6 +27,21 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
 	_set_cron_array( $crons );
 }
 
+/**
+ * Schedule a periodic event.
+ *
+ * Schedules a hook which will be executed by the WordPress actions core on a
+ * specific interval, specified by you. The action will trigger when someone
+ * visits your WordPress site, if the scheduled time has passed.
+ *
+ * @since 2.1.0
+ *
+ * @param int $timestamp Timestamp for when to run the event.
+ * @param string $recurrence How often the event should recur.
+ * @param callback $hook Function or method to call, when cron is run.
+ * @param array $args Optional. Arguments to pass to the hook function.
+ * @return bool|null False on failure, null when complete with scheduling event.
+ */
 function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array()) {
 	$crons = _get_cron_array();
 	$schedules = wp_get_schedules();
@@ -19,6 +53,17 @@ function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array()) {
 	_set_cron_array( $crons );
 }
 
+/**
+ * Reschedule a recurring event.
+ *
+ * @since 2.1.0
+ *
+ * @param int $timestamp Timestamp for when to run the event.
+ * @param string $recurrence How often the event should recur.
+ * @param callback $hook Function or method to call, when cron is run.
+ * @param array $args Optional. Arguments to pass to the hook function.
+ * @return bool|null False on failure. Null when event is rescheduled.
+ */
 function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array()) {
 	$crons = _get_cron_array();
 	$schedules = wp_get_schedules();
@@ -41,6 +86,18 @@ function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array()) {
 	wp_schedule_event( $timestamp, $recurrence, $hook, $args );
 }
 
+/**
+ * Unschedule a previously scheduled cron job.
+ *
+ * The $timestamp and $hook parameters are required, so that the event can be
+ * identified.
+ *
+ * @since 2.1.0
+ *
+ * @param int $timestamp Timestamp for when to run the event.
+ * @param callback $hook Function or method to call, when cron is run.
+ * @param array $args Optional. Arguments to pass to the hook function.
+ */
 function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
 	$crons = _get_cron_array();
 	$key = md5(serialize($args));
@@ -52,6 +109,14 @@ function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
 	_set_cron_array( $crons );
 }
 
+/**
+ * Unschedule all cron jobs attached to a specific hook.
+ *
+ * @since 2.1.0
+ *
+ * @param callback $hook Function or method to call, when cron is run.
+ * @param mixed $args,... Optional. Event arguments.
+ */
 function wp_clear_scheduled_hook( $hook ) {
 	$args = array_slice( func_get_args(), 1 );
 
@@ -59,6 +124,15 @@ function wp_clear_scheduled_hook( $hook ) {
 		wp_unschedule_event( $timestamp, $hook, $args );
 }
 
+/**
+ * Retrieve the next timestamp for a cron event.
+ *
+ * @since 2.1.0
+ *
+ * @param callback $hook Function or method to call, when cron is run.
+ * @param array $args Optional. Arguments to pass to the hook function.
+ * @return bool|int The UNIX timestamp of the next time the scheduled event will occur.
+ */
 function wp_next_scheduled( $hook, $args = array() ) {
 	$crons = _get_cron_array();
 	$key = md5(serialize($args));
@@ -76,7 +150,7 @@ function wp_next_scheduled( $hook, $args = array() ) {
  *
  * @since 2.1.0
  *
- * @return null CRON could not be spawned, because it is not needed to run.
+ * @return null Cron could not be spawned, because it is not needed to run.
  */
 function spawn_cron() {
 	$crons = _get_cron_array();
@@ -93,6 +167,13 @@ function spawn_cron() {
 	wp_remote_post($cron_url, array('timeout' => 0.01, 'blocking' => false));
 }
 
+/**
+ * Run scheduled callbacks or spawn cron for all scheduled events.
+ *
+ * @since 2.1.0
+ *
+ * @return null When doesn't need to run Cron.
+ */
 function wp_cron() {
 	// Prevent infinite loops caused by lack of wp-cron.php
 	if ( strpos($_SERVER['REQUEST_URI'], '/wp-cron.php') !== false )
@@ -119,6 +200,36 @@ function wp_cron() {
 	}
 }
 
+/**
+ * Retrieve supported and filtered Cron recurrences.
+ *
+ * The supported recurrences are 'hourly' and 'daily'. A plugin may add more by
+ * hooking into the 'cron_schedules' filter. The filter accepts an array of
+ * arrays. The outer array has a key that is the name of the schedule or for
+ * example 'weekly'. The value is an array with two keys, one is 'interval' and
+ * the other is 'display'.
+ *
+ * The 'interval' is a number in seconds of when the cron job should run. So for
+ * 'hourly', the time is 3600 or 60*60. For weekly, the value would be
+ * 60*60*24*7 or 604800. The value of 'interval' would then be 604800.
+ *
+ * The 'display' is the description. For the 'weekly' key, the 'display' would
+ * be <code>__('Once Weekly')</code>.
+ *
+ * For your plugin, you will be passed an array. you can easily add your
+ * schedule by doing the following.
+ * <code>
+ * // filter parameter variable name is 'array'
+ *	$array['weekly'] = array(
+ *		'interval' => 604800,
+ *		'display' => __('Once Weekly')
+ *	);
+ * </code>
+ *
+ * @since 2.1.0
+ *
+ * @return array
+ */
 function wp_get_schedules() {
 	$schedules = array(
 		'hourly' => array( 'interval' => 3600, 'display' => __('Once Hourly') ),
@@ -128,6 +239,15 @@ function wp_get_schedules() {
 	return array_merge( apply_filters( 'cron_schedules', array() ), $schedules );
 }
 
+/**
+ * Retrieve Cron schedule for hook with arguments.
+ *
+ * @since 2.1.0
+ *
+ * @param callback $hook Function or method to call, when cron is run.
+ * @param array $args Optional. Arguments to pass to the hook function.
+ * @return string|bool False, if no schedule. Schedule on success.
+ */
 function wp_get_schedule($hook, $args = array()) {
 	$crons = _get_cron_array();
 	$key = md5(serialize($args));
@@ -144,6 +264,14 @@ function wp_get_schedule($hook, $args = array()) {
 // Private functions
 //
 
+/**
+ * Retrieve cron info array option.
+ *
+ * @since 2.1.0
+ * @access private
+ *
+ * @return array CRON info array.
+ */
 function _get_cron_array()  {
 	$cron = get_option('cron');
 	if ( ! is_array($cron) )
@@ -157,11 +285,30 @@ function _get_cron_array()  {
 	return $cron;
 }
 
+/**
+ * Updates the CRON option with the new CRON array.
+ *
+ * @since 2.1.0
+ * @access private
+ *
+ * @param array $cron Cron info array from {@link _get_cron_array()}.
+ */
 function _set_cron_array($cron) {
 	$cron['version'] = 2;
 	update_option( 'cron', $cron );
 }
 
+/**
+ * Upgrade a Cron info array.
+ *
+ * This function upgrades the Cron info array to version 2.
+ *
+ * @since 2.1.0
+ * @access private
+ *
+ * @param array $cron Cron info array from {@link _get_cron_array()}.
+ * @return array An upgraded Cron info array.
+ */
 function _upgrade_cron_array($cron) {
 	if ( isset($cron['version']) && 2 == $cron['version'])
 		return $cron;