diff --git a/src/wp-includes/cron.php b/src/wp-includes/cron.php
index a4d160f70c..f7e444b83e 100644
--- a/src/wp-includes/cron.php
+++ b/src/wp-includes/cron.php
@@ -1,28 +1,28 @@
 <?php
 /**
- * WordPress CRON API
+ * WordPress Cron API
  *
  * @package WordPress
  */
 
 /**
- * Schedules a hook to run only once.
+ * Schedules an event to run only once.
  *
- * Schedules a hook which will be executed once by the WordPress actions core at
+ * Schedules an event which will execute 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.
  *
  * Note that scheduling an event to occur within 10 minutes of an existing event
- * with the same action hook will be ignored, unless you pass unique `$args` values
+ * with the same action hook will be ignored unless you pass unique `$args` values
  * for each scheduled event.
  *
  * @since 2.1.0
  * @link https://codex.wordpress.org/Function_Reference/wp_schedule_single_event
  *
- * @param int $timestamp Timestamp for when to run the event.
- * @param string $hook Action hook to execute when cron is run.
+ * @param int $timestamp Unix timestamp (UTC) for when to run the event.
+ * @param string $hook Action hook to execute when event is run.
  * @param array $args Optional. Arguments to pass to the hook's callback function.
- * @return false|void False when an event is not scheduled.
+ * @return false|void False if the event does not get scheduled.
  */
 function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
 	// Make sure timestamp is a positive integer
@@ -43,7 +43,14 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
 	 *
 	 * @since 3.1.0
 	 *
-	 * @param object $event An object containing an event's data.
+	 * @param stdClass $event {
+	 *     An object containing an event's data.
+	 *
+	 *     @type string       $hook      Action hook to execute when event is run.
+	 *     @type int          $timestamp Unix timestamp (UTC) for when to run the event.
+	 *     @type string|false $schedule  How often the event should recur. See `wp_get_schedules()`.
+	 *     @type array        $args      Arguments to pass to the hook's callback function.
+	 * }
 	 */
 	$event = apply_filters( 'schedule_event', $event );
 
@@ -59,24 +66,24 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
 }
 
 /**
- * Schedule a periodic event.
+ * Schedule a recurring 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.
  *
- * Valid values for the recurrence are hourly, daily and twicedaily. These can
+ * Valid values for the recurrence are hourly, daily, and twicedaily. These can
  * be extended using the {@see 'cron_schedules'} filter in wp_get_schedules().
  *
  * Use wp_next_scheduled() to prevent duplicates
  *
  * @since 2.1.0
  *
- * @param int $timestamp Timestamp for when to run the event.
+ * @param int $timestamp Unix timestamp (UTC) for when to run the event.
  * @param string $recurrence How often the event should recur.
- * @param string $hook Action hook to execute when cron is run.
+ * @param string $hook Action hook to execute when event is run.
  * @param array $args Optional. Arguments to pass to the hook's callback function.
- * @return false|void False when an event is not scheduled.
+ * @return false|void False if the event does not get scheduled.
  */
 function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array()) {
 	// Make sure timestamp is a positive integer
@@ -110,11 +117,11 @@ function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array()) {
  *
  * @since 2.1.0
  *
- * @param int $timestamp Timestamp for when to run the event.
+ * @param int $timestamp Unix timestamp (UTC) for when to run the event.
  * @param string $recurrence How often the event should recur.
- * @param string $hook Action hook to execute when cron is run.
+ * @param string $hook Action hook to execute when event is run.
  * @param array $args Optional. Arguments to pass to the hook's callback function.
- * @return false|void False when an event is not scheduled.
+ * @return false|void False if the event does not get rescheduled.
  */
 function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
 	// Make sure timestamp is a positive integer
@@ -152,20 +159,20 @@ function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array() )
 }
 
 /**
- * Unschedule a previously scheduled cron job.
+ * Unschedule a previously scheduled event.
  *
- * The $timestamp and $hook parameters are required, so that the event can be
+ * 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 int $timestamp Unix timestamp (UTC) for when to run the event.
  * @param string $hook Action hook, the execution of which will be unscheduled.
  * @param array $args Arguments to pass to the hook's callback function.
  * Although not passed to a callback function, these arguments are used
  * to uniquely identify the scheduled event, so they should be the same
  * as those used when originally scheduling the event.
- * @return false|void False when an event is not unscheduled.
+ * @return false|void False if the event does not get unscheduled.
  */
 function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
 	// Make sure timestamp is a positive integer
@@ -184,12 +191,12 @@ function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
 }
 
 /**
- * Unschedule all cron jobs attached to a specific hook.
+ * Unschedule all events attached to the specified hook.
  *
  * @since 2.1.0
  *
  * @param string $hook Action hook, the execution of which will be unscheduled.
- * @param array $args Optional. Arguments that were to be pass to the hook's callback function.
+ * @param array $args Optional. Arguments that were to be passed to the hook's callback function.
  */
 function wp_clear_scheduled_hook( $hook, $args = array() ) {
 	// Backward compatibility
@@ -215,13 +222,13 @@ function wp_clear_scheduled_hook( $hook, $args = array() ) {
 }
 
 /**
- * Retrieve the next timestamp for a cron event.
+ * Retrieve the next timestamp for an event.
  *
  * @since 2.1.0
  *
- * @param string $hook Action hook to execute when cron is run.
+ * @param string $hook Action hook to execute when event is run.
  * @param array $args Optional. Arguments to pass to the hook's callback function.
- * @return false|int The UNIX timestamp of the next time the scheduled event will occur.
+ * @return false|int The Unix timestamp of the next time the scheduled event will occur.
  */
 function wp_next_scheduled( $hook, $args = array() ) {
 	$crons = _get_cron_array();
@@ -240,7 +247,7 @@ function wp_next_scheduled( $hook, $args = array() ) {
  *
  * @since 2.1.0
  *
- * @param int $gmt_time Optional. Unix timestamp. Default 0 (current time is used).
+ * @param int $gmt_time Optional. Unix timestamp (UTC). Default 0 (current time is used).
  */
 function spawn_cron( $gmt_time = 0 ) {
 	if ( ! $gmt_time )
@@ -250,7 +257,7 @@ function spawn_cron( $gmt_time = 0 ) {
 		return;
 
 	/*
-	 * Get the cron lock, which is a unix timestamp of when the last cron was spawned
+	 * Get the cron lock, which is a Unix timestamp of when the last cron was spawned
 	 * and has not finished running.
 	 *
 	 * Multiple processes on multiple web servers can run this code concurrently,
@@ -364,11 +371,11 @@ function wp_cron() {
 }
 
 /**
- * Retrieve supported and filtered Cron recurrences.
+ * Retrieve supported event recurrence schedules.
  *
- * The supported recurrences are 'hourly' and 'daily'. A plugin may add more by
- * hooking into the {@see '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
+ * The default supported recurrences are 'hourly', 'twicedaily', and 'daily'. A plugin may
+ * add more by hooking into the {@see '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'.
  *
@@ -410,13 +417,15 @@ function wp_get_schedules() {
 }
 
 /**
- * Retrieve Cron schedule for hook with arguments.
+ * Retrieve the recurrence schedule for an event.
+ *
+ * @see wp_get_schedules() for available schedules.
  *
  * @since 2.1.0
  *
- * @param string $hook Action hook to execute when cron is run.
- * @param array $args Optional. Arguments to pass to the hook's callback function.
- * @return string|false False, if no schedule. Schedule on success.
+ * @param string $hook Action hook to identify the event.
+ * @param array $args Optional. Arguments passed to the event's callback function.
+ * @return string|false False, if no schedule. Schedule name on success.
  */
 function wp_get_schedule($hook, $args = array()) {
 	$crons = _get_cron_array();