diff --git src/wp-includes/cron.php src/wp-includes/cron.php
index fbf5a629af..7a147433dd 100644
--- src/wp-includes/cron.php
+++ src/wp-includes/cron.php
@@ -26,7 +26,7 @@
  * @param int    $timestamp  Unix timestamp (UTC) for when to next run the event.
  * @param string $hook       Action hook to execute when the event is run.
  * @param array  $args       Optional. Array containing each separate argument to pass to the hook's callback function.
- * @return false|void False if the event did not get scheduled.
+ * @return bool Whether or not the requested event has been scheduled.
  */
 function wp_schedule_single_event( $timestamp, $hook, $args = array() ) {
 	// Make sure timestamp is a positive integer
@@ -34,13 +34,6 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array() ) {
 		return false;
 	}
 
-	// Don't schedule a duplicate if there's already an identical event due within 10 minutes of it
-	$next = wp_next_scheduled( $hook, $args );
-	if ( $next && abs( $next - $timestamp ) <= 10 * MINUTE_IN_SECONDS ) {
-		return false;
-	}
-
-	$crons = _get_cron_array();
 	$event = (object) array(
 		'hook'      => $hook,
 		'timestamp' => $timestamp,
@@ -48,6 +41,45 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array() ) {
 		'args'      => $args,
 	);
 
+	/**
+	 * Filter to preflight or hijack scheduling an event.
+	 *
+	 * Passing a non-null value will short-circuit adding the event to the cron
+	 * array, returning the passed value instead.
+	 *
+	 * Both single events and recurring events are passed through this filter;
+	 * single events have `$event->schedule` as false, whereas recurring events
+	 * have this set to a recurrence from {@see wp_get_schedules}. Recurring
+	 * events also have the integer recurrence interval set as `$event->interval`.
+	 *
+	 * Before scheduling, it is recommended you check for an identical event
+	 * within ten minutes and apply the {@see schedule_event} filter to check
+	 * if another plugin has disallowed the event.
+	 *
+	 * Pass true if the event was successfully scheduled, false if not.
+	 *
+	 * @param null|bool $pre   Value to return instead. Default null to continue adding the event.
+	 * @param stdClass  $event {
+	 *     An object containing an event's data.
+	 *
+	 *     @type string       $hook      Action hook to execute when the event is run.
+	 *     @type int          $timestamp Unix timestamp (UTC) for when to next run the event.
+	 *     @type string|false $schedule  How often the event should subsequently recur.
+	 *     @type array        $args      Array containing each separate argument to pass to the hook's callback function.
+	 *     @type int          $interval  The interval time in seconds for the schedule. Only present for recurring events.
+	 * }
+	 */
+	$pre = apply_filters( 'pre_schedule_event', null, $event );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
+	// Don't schedule a duplicate if there's already an identical event due within 10 minutes of it
+	$next = wp_next_scheduled( $hook, $args );
+	if ( $next && abs( $next - $timestamp ) <= 10 * MINUTE_IN_SECONDS ) {
+		return false;
+	}
+
 	/**
 	 * Filters a single event before it is scheduled.
 	 *
@@ -72,12 +104,13 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array() ) {
 
 	$key = md5( serialize( $event->args ) );
 
+	$crons = _get_cron_array();
 	$crons[ $event->timestamp ][ $event->hook ][ $key ] = array(
 		'schedule' => $event->schedule,
 		'args'     => $event->args,
 	);
 	uksort( $crons, 'strnatcasecmp' );
-	_set_cron_array( $crons );
+	return _set_cron_array( $crons );
 }
 
 /**
@@ -105,7 +138,7 @@ function wp_schedule_single_event( $timestamp, $hook, $args = array() ) {
  * @param string $recurrence How often the event should subsequently recur. See wp_get_schedules() for accepted values.
  * @param string $hook       Action hook to execute when the event is run.
  * @param array  $args       Optional. Array containing each separate argument to pass to the hook's callback function.
- * @return false|void False if the event did not get scheduled.
+ * @return bool Whether or not the requested event has been scheduled.
  */
 function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
 	// Make sure timestamp is a positive integer
@@ -113,7 +146,6 @@ function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
 		return false;
 	}
 
-	$crons     = _get_cron_array();
 	$schedules = wp_get_schedules();
 
 	if ( ! isset( $schedules[ $recurrence ] ) ) {
@@ -127,6 +159,13 @@ function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
 		'args'      => $args,
 		'interval'  => $schedules[ $recurrence ]['interval'],
 	);
+
+	/** This filter is documented in wp-includes/cron.php */
+	$pre = apply_filters( 'pre_schedule_event', null, $event );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
 	/** This filter is documented in wp-includes/cron.php */
 	$event = apply_filters( 'schedule_event', $event );
 
@@ -137,13 +176,14 @@ function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
 
 	$key = md5( serialize( $event->args ) );
 
+	$crons = _get_cron_array();
 	$crons[ $event->timestamp ][ $event->hook ][ $key ] = array(
 		'schedule' => $event->schedule,
 		'args'     => $event->args,
 		'interval' => $event->interval,
 	);
 	uksort( $crons, 'strnatcasecmp' );
-	_set_cron_array( $crons );
+	return _set_cron_array( $crons );
 }
 
 /**
@@ -155,7 +195,7 @@ function wp_schedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
  * @param string $recurrence How often the event should subsequently recur. See wp_get_schedules() for accepted values.
  * @param string $hook       Action hook to execute when the event is run.
  * @param array  $args       Optional. Array containing each separate argument to pass to the hook's callback function.
- * @return false|void False if the event did not get rescheduled.
+ * @return bool Whether or not the requested event has been rescheduled.
  */
 function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array() ) {
 	// Make sure timestamp is a positive integer
@@ -163,19 +203,54 @@ function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array() )
 		return false;
 	}
 
-	$crons     = _get_cron_array();
 	$schedules = wp_get_schedules();
-	$key       = md5( serialize( $args ) );
 	$interval  = 0;
 
-	// First we try to get it from the schedule
+	// First we try to get the interval from the schedule.
 	if ( isset( $schedules[ $recurrence ] ) ) {
 		$interval = $schedules[ $recurrence ]['interval'];
 	}
-	// Now we try to get it from the saved interval in case the schedule disappears
-	if ( 0 == $interval ) {
-		$interval = $crons[ $timestamp ][ $hook ][ $key ]['interval'];
+
+	// Now we try to get it from the saved interval in case the schedule disappears.
+	if ( 0 === $interval ) {
+		$scheduled_event = wp_get_scheduled_event( $hook, $args, $timestamp );
+		if ( $scheduled_event && isset( $scheduled_event->interval ) ) {
+			$interval = $scheduled_event->interval;
+		}
 	}
+
+	$event = (object) array(
+		'hook'      => $hook,
+		'timestamp' => $timestamp,
+		'schedule'  => $recurrence,
+		'args'      => $args,
+		'interval'  => $interval,
+	);
+
+	/**
+	 * Filter to preflight or hijack rescheduling of events.
+	 *
+	 * Passing a non-null value will short-circuit the normal rescheduling
+	 * process, returning the passed value instead.
+	 *
+	 * Pass true if the event was successfully scheduled, false if not.
+	 *
+	 * @param null|bool $pre   Value to return instead. Default null to continue adding the event.
+	 * @param stdClass  $event {
+	 *     An object containing an event's data.
+	 *
+	 *     @type string       $hook      Action hook to execute when the event is run.
+	 *     @type int          $timestamp Unix timestamp (UTC) for when to next run the event.
+	 *     @type string|false $schedule  How often the event should subsequently recur.
+	 *     @type array        $args      Array containing each separate argument to pass to the hook's callback function.
+	 *     @type int          $interval  The interval time in seconds for the schedule. Only present for recurring events.
+	 * }
+	 */
+	$pre = apply_filters( 'pre_reschedule_event', null, $event );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
 	// Now we assume something is wrong and fail to schedule
 	if ( 0 == $interval ) {
 		return false;
@@ -189,7 +264,7 @@ function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array() )
 		$timestamp = $now + ( $interval - ( ( $now - $timestamp ) % $interval ) );
 	}
 
-	wp_schedule_event( $timestamp, $recurrence, $hook, $args );
+	return wp_schedule_event( $timestamp, $recurrence, $hook, $args );
 }
 
 /**
@@ -205,7 +280,7 @@ function wp_reschedule_event( $timestamp, $recurrence, $hook, $args = array() )
  * @param array  $args      Optional. Array containing each separate argument to pass to the hook's callback function.
  *                          Although not passed to a callback, these arguments are used to uniquely identify the
  *                          event, so they should be the same as those used when originally scheduling the event.
- * @return false|void False if the event did not get unscheduled.
+ * @return bool Whether or not the requested event has been unscheduled.
  */
 function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
 	// Make sure timestamp is a positive integer
@@ -213,6 +288,24 @@ function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
 		return false;
 	}
 
+	/**
+	 * Filter to preflight or hijack unscheduling of events.
+	 *
+	 * Passing a non-null value will short-circuit the normal unscheduling
+	 * process, returning the passed value instead.
+	 *
+	 * Pass true if the event was successfully unscheduled, false if not.
+	 *
+	 * @param null|bool $pre       Value to return instead. Default null to continue unscheduling the event.
+	 * @param int       $timestamp Timestamp 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.
+	 */
+	$pre = apply_filters( 'pre_unschedule_event', null, $timestamp, $hook, $args );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
 	$crons = _get_cron_array();
 	$key   = md5( serialize( $args ) );
 	unset( $crons[ $timestamp ][ $hook ][ $key ] );
@@ -222,7 +315,7 @@ function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
 	if ( empty( $crons[ $timestamp ] ) ) {
 		unset( $crons[ $timestamp ] );
 	}
-	_set_cron_array( $crons );
+	return _set_cron_array( $crons );
 }
 
 /**
@@ -232,6 +325,7 @@ function wp_unschedule_event( $timestamp, $hook, $args = array() ) {
  *
  * @param string $hook Action hook, the execution of which will be unscheduled.
  * @param array $args Optional. Arguments that were to be passed to the hook's callback function.
+ * @return array Boolean values, indicating the result of attempting to unschedule each indicated event, with timestamps as keys.
  */
 function wp_clear_scheduled_hook( $hook, $args = array() ) {
 	// Backward compatibility
@@ -241,20 +335,40 @@ function wp_clear_scheduled_hook( $hook, $args = array() ) {
 		$args = array_slice( func_get_args(), 1 );
 	}
 
+	/**
+	 * Filter to preflight or hijack clearing a scheduled hook.
+	 *
+	 * Passing a non-null value will short-circuit the normal unscheduling
+	 * process, returning the passed value instead.
+	 *
+	 * Pass an empty array if no events are unscheduled, an array of boolean
+	 * values if events are unscheduled see {@see wp_clear_scheduled_hook}.
+	 *
+	 * @param null|array $pre  Value to return instead. Default null to continue unscheduling 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.
+	 */
+	$pre = apply_filters( 'pre_clear_scheduled_hook', null, $hook, $args );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
 	// This logic duplicates wp_next_scheduled()
 	// It's required due to a scenario where wp_unschedule_event() fails due to update_option() failing,
 	// and, wp_next_scheduled() returns the same schedule in an infinite loop.
 	$crons = _get_cron_array();
 	if ( empty( $crons ) ) {
-		return;
+		return array();
 	}
 
-	$key = md5( serialize( $args ) );
+	$results = array();
+	$key     = md5( serialize( $args ) );
 	foreach ( $crons as $timestamp => $cron ) {
 		if ( isset( $cron[ $hook ][ $key ] ) ) {
-			wp_unschedule_event( $timestamp, $hook, $args );
+			$results[ $timestamp ] = wp_unschedule_event( $timestamp, $hook, $args );
 		}
 	}
+	return $results;
 }
 
 /**
@@ -265,8 +379,25 @@ function wp_clear_scheduled_hook( $hook, $args = array() ) {
  * @since 4.9.0
  *
  * @param string $hook Action hook, the execution of which will be unscheduled.
+ * @return bool Whether or not the requested events have been unscheduled.
  */
 function wp_unschedule_hook( $hook ) {
+	/**
+	 * Filter to preflight or hijack clearing all events attached to the hook.
+	 *
+	 * Passing a non-null value will short-circuit the normal unscheduling
+	 * process, returning the passed value instead.
+	 *
+	 * Pass true if events are cleared, false if not.
+	 *
+	 * @param null|array $pre  Value to return instead. Default null to continue unscheduling the hook.
+	 * @param string     $hook Action hook, the execution of which will be unscheduled.
+	 */
+	$pre = apply_filters( 'pre_unschedule_hook', null, $hook );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
 	$crons = _get_cron_array();
 
 	foreach ( $crons as $timestamp => $args ) {
@@ -277,7 +408,72 @@ function wp_unschedule_hook( $hook ) {
 		}
 	}
 
-	_set_cron_array( $crons );
+	return _set_cron_array( $crons );
+}
+
+/**
+ * Retrieve a scheduled event.
+ *
+ * Retrieve the full event object for a given event.
+ *
+ * @param string   $hook      Action hook of the event.
+ * @param array    $args      Optional. Array containing each separate argument to pass to the hook's callback function.
+ *                            Although not passed to a callback, these arguments are used to uniquely identify the
+ *                            event, so they should be the same as those used when originally scheduling the event.
+ * @param int|null $timestamp Optional. Unix timestamp (UTC) of the event. If not specified, the next scheduled event is returned.
+ * @return bool|object The event object. False if the event does not exist.
+ */
+function wp_get_scheduled_event( $hook, $args = array(), $timestamp = null ) {
+	if ( ! $timestamp ) {
+		// Get the next scheduled event.
+		$timestamp = wp_next_scheduled( $hook, $args );
+	}
+
+	/**
+	 * Filter to preflight or hijack retrieving a scheduled event.
+	 *
+	 * Passing a non-null value will short-circuit the normal
+	 * process, returning the passed value instead.
+	 *
+	 * Pass false if the event does not exist, otherwise an event object
+	 * should be returned.
+	 *
+	 * @param null|bool $pre       Value to return instead. Default null to continue retrieving the event.
+	 * @param string    $hook      Action hook of the event.
+	 * @param array     $args      Array containing each separate argument to pass to the hook's callback function.
+	 *                             Although not passed to a callback, these arguments are used to uniquely identify the
+	 *                             event.
+	 * @param int       $timestamp Unix timestamp (UTC) of the event.
+	 */
+	$pre = apply_filters( 'pre_get_scheduled_event', null, $hook, $args, $timestamp );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
+	$crons = _get_cron_array();
+	$key   = md5( serialize( $args ) );
+
+	if ( ! $timestamp || ! isset( $crons[ $timestamp ] ) ) {
+		// No such event.
+		return false;
+	}
+
+	if ( ! isset( $crons[ $timestamp ][ $hook ] ) || ! isset( $crons[ $timestamp ][ $hook ][ $key ] ) ) {
+		return false;
+	}
+
+	$event = (object) array(
+		'hook'      => $hook,
+		'timestamp' => $timestamp,
+		'schedule'  => $crons[ $timestamp ][ $hook ][ $key ]['schedule'],
+		'args'      => $args,
+	);
+
+	if ( isset( $crons[ $timestamp ][ $hook ][ $key ]['interval'] ) ) {
+		$event->interval = $crons[ $timestamp ][ $hook ][ $key ]['interval'];
+	}
+
+	return $event;
 }
 
 /**
@@ -292,17 +488,44 @@ function wp_unschedule_hook( $hook ) {
  * @return false|int The Unix timestamp of the next time the event will occur. False if the event doesn't exist.
  */
 function wp_next_scheduled( $hook, $args = array() ) {
+	/**
+	 * Filter to preflight or hijack retrieving the next scheduled event timestamp.
+	 *
+	 * Passing a non-null value will short-circuit the normal retrieval
+	 * process, returning the passed value instead.
+	 *
+	 * Pass the timestamp of the next event if it exists, false if not.
+	 *
+	 * @param null|bool $pre       Value to return instead. Default null to continue unscheduling the event.
+	 * @param string    $hook      Action hook of the event.
+	 * @param array     $args      Arguments to pass to the hook's callback function.
+	 */
+	$pre = apply_filters( 'pre_next_scheduled', null, $hook, $args );
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
 	$crons = _get_cron_array();
 	$key   = md5( serialize( $args ) );
-	if ( empty( $crons ) ) {
-		return false;
-	}
-	foreach ( $crons as $timestamp => $cron ) {
-		if ( isset( $cron[ $hook ][ $key ] ) ) {
-			return $timestamp;
+	$next  = false;
+
+	if ( ! empty( $crons ) ) {
+		foreach ( $crons as $timestamp => $cron ) {
+			if ( isset( $cron[ $hook ][ $key ] ) ) {
+				$next = $timestamp;
+				break;
+			}
 		}
 	}
-	return false;
+
+	/**
+	 * Filter the next scheduled event timestamp.
+	 *
+	 * @param int|bool $next The UNIX timestamp when the scheduled event will next occur, or false if not found.
+	 * @param string   $hook Action hook to execute when cron is run.
+	 * @param array    $args Arguments to be passed to the callback function. Used for deduplicating events.
+	 */
+	return apply_filters( 'next_scheduled', $next, $hook, $args );
 }
 
 /**
@@ -311,6 +534,8 @@ function wp_next_scheduled( $hook, $args = array() ) {
  * @since 2.1.0
  *
  * @param int $gmt_time Optional. Unix timestamp (UTC). Default 0 (current time is used).
+ * @return null|WP_Error|array Null when cron could not be spawned, because it is not needed to run.
+ *                             When cron runs, return the result of {@see wp_remote_post}
  */
 function spawn_cron( $gmt_time = 0 ) {
 	if ( ! $gmt_time ) {
@@ -318,7 +543,7 @@ function spawn_cron( $gmt_time = 0 ) {
 	}
 
 	if ( defined( 'DOING_CRON' ) || isset( $_GET['doing_wp_cron'] ) ) {
-		return;
+		return null;
 	}
 
 	/*
@@ -336,23 +561,23 @@ function spawn_cron( $gmt_time = 0 ) {
 
 	// don't run if another process is currently running it or more than once every 60 sec.
 	if ( $lock + WP_CRON_LOCK_TIMEOUT > $gmt_time ) {
-		return;
+		return null;
 	}
 
 	//sanity check
 	$crons = _get_cron_array();
 	if ( ! is_array( $crons ) ) {
-		return;
+		return null;
 	}
 
 	$keys = array_keys( $crons );
 	if ( isset( $keys[0] ) && $keys[0] > $gmt_time ) {
-		return;
+		return null;
 	}
 
 	if ( defined( 'ALTERNATE_WP_CRON' ) && ALTERNATE_WP_CRON ) {
 		if ( 'GET' !== $_SERVER['REQUEST_METHOD'] || defined( 'DOING_AJAX' ) || defined( 'XMLRPC_REQUEST' ) ) {
-			return;
+			return null;
 		}
 
 		$doing_wp_cron = sprintf( '%.22F', $gmt_time );
@@ -368,7 +593,7 @@ function spawn_cron( $gmt_time = 0 ) {
 		flush();
 
 		WP_DEBUG ? include_once( ABSPATH . 'wp-cron.php' ) : @include_once( ABSPATH . 'wp-cron.php' );
-		return;
+		return null;
 	}
 
 	// Set the cron lock with the current unix timestamp, when the cron is being spawned.
@@ -409,30 +634,34 @@ function spawn_cron( $gmt_time = 0 ) {
 		), $doing_wp_cron
 	);
 
-	wp_remote_post( $cron_request['url'], $cron_request['args'] );
+	return wp_remote_post( $cron_request['url'], $cron_request['args'] );
 }
 
 /**
  * Run scheduled callbacks or spawn cron for all scheduled events.
  *
  * @since 2.1.0
+ *
+ * @return array Array of spawn_cron() results for any cron jobs that were run, with cron timestamps as keys.
  */
 function wp_cron() {
 	// Prevent infinite loops caused by lack of wp-cron.php
 	if ( strpos( $_SERVER['REQUEST_URI'], '/wp-cron.php' ) !== false || ( defined( 'DISABLE_WP_CRON' ) && DISABLE_WP_CRON ) ) {
-		return;
+		return array();
 	}
 
-	if ( false === $crons = _get_cron_array() ) {
-		return;
+	$crons = _get_cron_array();
+	if ( false === $crons ) {
+		return array();
 	}
 
 	$gmt_time = microtime( true );
 	$keys     = array_keys( $crons );
 	if ( isset( $keys[0] ) && $keys[0] > $gmt_time ) {
-		return;
+		return array();
 	}
 
+	$results   = array();
 	$schedules = wp_get_schedules();
 	foreach ( $crons as $timestamp => $cronhooks ) {
 		if ( $timestamp > $gmt_time ) {
@@ -442,10 +671,12 @@ function wp_cron() {
 			if ( isset( $schedules[ $hook ]['callback'] ) && ! call_user_func( $schedules[ $hook ]['callback'] ) ) {
 				continue;
 			}
-			spawn_cron( $gmt_time );
+			$results[ $timestamp ] = spawn_cron( $gmt_time );
 			break 2;
 		}
 	}
+
+	return $results;
 }
 
 /**
@@ -514,17 +745,21 @@ function wp_get_schedules() {
  * @return string|false False, if no schedule. Schedule name on success.
  */
 function wp_get_schedule( $hook, $args = array() ) {
-	$crons = _get_cron_array();
-	$key   = md5( serialize( $args ) );
-	if ( empty( $crons ) ) {
-		return false;
-	}
-	foreach ( $crons as $timestamp => $cron ) {
-		if ( isset( $cron[ $hook ][ $key ] ) ) {
-			return $cron[ $hook ][ $key ]['schedule'];
-		}
+	$schedule = false;
+	$event    = wp_get_scheduled_event( $hook, $args );
+
+	if ( $event ) {
+		$schedule = $event->schedule;
 	}
-	return false;
+
+	/**
+	 * Filter the schedule for a hook.
+	 *
+	 * @param string|bool $schedule Schedule for the hook. False if not found.
+	 * @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 apply_filters( 'get_schedule', $schedule, $hook, $args );
 }
 
 //
@@ -561,10 +796,11 @@ function _get_cron_array() {
  * @access private
  *
  * @param array $cron Cron info array from _get_cron_array().
+ * @return bool Whether the update of the cron option succeeded (according to {@see update_option})
  */
 function _set_cron_array( $cron ) {
 	$cron['version'] = 2;
-	update_option( 'cron', $cron );
+	return update_option( 'cron', $cron );
 }
 
 /**