diff --git a/apps/dav/appinfo/v1/caldav.php b/apps/dav/appinfo/v1/caldav.php
index ba49f2961f42e..9f12a92f4cdba 100644
--- a/apps/dav/appinfo/v1/caldav.php
+++ b/apps/dav/appinfo/v1/caldav.php
@@ -46,10 +46,10 @@
 	'principals/'
 );
 $db = \OC::$server->getDatabaseConnection();
-$config = \OC::$server->getConfig();
 $userManager = \OC::$server->getUserManager();
 $random = \OC::$server->getSecureRandom();
-$calDavBackend = new CalDavBackend($db, $principalBackend, $userManager, $config, $random);
+$dispatcher = \OC::$server->getEventDispatcher();
+$calDavBackend = new CalDavBackend($db, $principalBackend, $userManager, $random, $dispatcher);
 
 $debugging = \OC::$server->getConfig()->getSystemValue('debug', false);
 
diff --git a/apps/dav/lib/AppInfo/Application.php b/apps/dav/lib/AppInfo/Application.php
index 2bdcff9cf84a5..c777f5e5a352e 100644
--- a/apps/dav/lib/AppInfo/Application.php
+++ b/apps/dav/lib/AppInfo/Application.php
@@ -24,6 +24,8 @@
  */
 namespace OCA\DAV\AppInfo;
 
+use OCA\DAV\CalDAV\Activity\Backend;
+use OCA\DAV\CalDAV\Activity\Extension;
 use OCA\DAV\CalDAV\BirthdayService;
 use OCA\DAV\Capabilities;
 use OCA\DAV\CardDAV\ContactsManager;
@@ -88,6 +90,67 @@ public function registerHooks() {
 				);
 			}
 		});
+
+		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::createCalendar', function(GenericEvent $event) {
+			/** @var Backend $backend */
+			$backend = $this->getContainer()->query(Backend::class);
+			$backend->onCalendarAdd(
+				$event->getArgument('calendarData')
+			);
+		});
+		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::updateCalendar', function(GenericEvent $event) {
+			/** @var Backend $backend */
+			$backend = $this->getContainer()->query(Backend::class);
+			$backend->onCalendarUpdate(
+				$event->getArgument('calendarData'),
+				$event->getArgument('shares'),
+				$event->getArgument('propertyMutations')
+			);
+		});
+		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendar', function(GenericEvent $event) {
+			/** @var Backend $backend */
+			$backend = $this->getContainer()->query(Backend::class);
+			$backend->onCalendarDelete(
+				$event->getArgument('calendarData'),
+				$event->getArgument('shares')
+			);
+		});
+		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::updateShares', function(GenericEvent $event) {
+			/** @var Backend $backend */
+			$backend = $this->getContainer()->query(Backend::class);
+			$backend->onCalendarUpdateShares(
+				$event->getArgument('calendarData'),
+				$event->getArgument('shares'),
+				$event->getArgument('add'),
+				$event->getArgument('remove')
+			);
+		});
+
+		$listener = function(GenericEvent $event, $eventName) {
+			/** @var Backend $backend */
+			$backend = $this->getContainer()->query(Backend::class);
+
+			$subject = Extension::SUBJECT_OBJECT_ADD;
+			if ($eventName === '\OCA\DAV\CalDAV\CalDavBackend::updateCalendarObject') {
+				$subject = Extension::SUBJECT_OBJECT_UPDATE;
+			} else if ($eventName === '\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject') {
+				$subject = Extension::SUBJECT_OBJECT_DELETE;
+			}
+			$backend->onTouchCalendarObject(
+				$subject,
+				$event->getArgument('calendarData'),
+				$event->getArgument('shares'),
+				$event->getArgument('objectData')
+			);
+		};
+		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject', $listener);
+		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::updateCalendarObject', $listener);
+		$dispatcher->addListener('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject', $listener);
+
+		$aM = $this->getContainer()->getServer()->getActivityManager();
+		$aM->registerExtension(function() {
+			return $this->getContainer()->query(Extension::class);
+		});
 	}
 
 	public function getSyncService() {
diff --git a/apps/dav/lib/CalDAV/Activity/Backend.php b/apps/dav/lib/CalDAV/Activity/Backend.php
new file mode 100644
index 0000000000000..6cf09f6de468a
--- /dev/null
+++ b/apps/dav/lib/CalDAV/Activity/Backend.php
@@ -0,0 +1,466 @@
+<?php
+/**
+ * @copyright Copyright (c) 2016 Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\DAV\CalDAV\Activity;
+
+
+use OCP\Activity\IEvent;
+use OCP\Activity\IManager as IActivityManager;
+use OCP\IGroup;
+use OCP\IGroupManager;
+use OCP\IUser;
+use OCP\IUserSession;
+use Sabre\VObject\Reader;
+
+/**
+ * Class Backend
+ *
+ * @package OCA\DAV\CalDAV\Activity
+ */
+class Backend {
+
+	/** @var IActivityManager */
+	protected $activityManager;
+
+	/** @var IGroupManager */
+	protected $groupManager;
+
+	/** @var IUserSession */
+	protected $userSession;
+
+	/**
+	 * @param IActivityManager $activityManager
+	 * @param IGroupManager $groupManager
+	 * @param IUserSession $userSession
+	 */
+	public function __construct(IActivityManager $activityManager, IGroupManager $groupManager, IUserSession $userSession) {
+		$this->activityManager = $activityManager;
+		$this->groupManager = $groupManager;
+		$this->userSession = $userSession;
+	}
+
+	/**
+	 * Creates activities when a calendar was creates
+	 *
+	 * @param array $calendarData
+	 */
+	public function onCalendarAdd(array $calendarData) {
+		$this->triggerCalendarActivity(Extension::SUBJECT_ADD, $calendarData);
+	}
+
+	/**
+	 * Creates activities when a calendar was updated
+	 *
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @param array $properties
+	 */
+	public function onCalendarUpdate(array $calendarData, array $shares, array $properties) {
+		$this->triggerCalendarActivity(Extension::SUBJECT_UPDATE, $calendarData, $shares, $properties);
+	}
+
+	/**
+	 * Creates activities when a calendar was deleted
+	 *
+	 * @param array $calendarData
+	 * @param array $shares
+	 */
+	public function onCalendarDelete(array $calendarData, array $shares) {
+		$this->triggerCalendarActivity(Extension::SUBJECT_DELETE, $calendarData, $shares);
+	}
+
+	/**
+	 * Creates activities for all related users when a calendar was touched
+	 *
+	 * @param string $action
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @param array $changedProperties
+	 */
+	protected function triggerCalendarActivity($action, array $calendarData, array $shares = [], array $changedProperties = []) {
+		if (!isset($calendarData['principaluri'])) {
+			return;
+		}
+
+		$principal = explode('/', $calendarData['principaluri']);
+		$owner = $principal[2];
+
+		$currentUser = $this->userSession->getUser();
+		if ($currentUser instanceof IUser) {
+			$currentUser = $currentUser->getUID();
+		} else {
+			$currentUser = $owner;
+		}
+
+		$event = $this->activityManager->generateEvent();
+		$event->setApp('dav')
+			->setObject(Extension::CALENDAR, $calendarData['id'])
+			->setType(Extension::CALENDAR)
+			->setAuthor($currentUser);
+
+		$changedVisibleInformation = array_intersect([
+			'{DAV:}displayname',
+			'{http://apple.com/ns/ical/}calendar-color'
+		], array_keys($changedProperties));
+
+		if (empty($shares) || ($action === Extension::SUBJECT_UPDATE && empty($changedVisibleInformation))) {
+			$users = [$owner];
+		} else {
+			$users = $this->getUsersForShares($shares);
+			$users[] = $owner;
+		}
+
+		foreach ($users as $user) {
+			$event->setAffectedUser($user)
+				->setSubject(
+					$user === $currentUser ? $action . '_self' : $action,
+					[
+						$currentUser,
+						$calendarData['{DAV:}displayname'],
+					]
+				);
+			$this->activityManager->publish($event);
+		}
+	}
+
+	/**
+	 * Creates activities for all related users when a calendar was (un-)shared
+	 *
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @param array $add
+	 * @param array $remove
+	 */
+	public function onCalendarUpdateShares(array $calendarData, array $shares, array $add, array $remove) {
+		$principal = explode('/', $calendarData['principaluri']);
+		$owner = $principal[2];
+
+		$currentUser = $this->userSession->getUser();
+		if ($currentUser instanceof IUser) {
+			$currentUser = $currentUser->getUID();
+		} else {
+			$currentUser = $owner;
+		}
+
+		$event = $this->activityManager->generateEvent();
+		$event->setApp('dav')
+			->setObject(Extension::CALENDAR, $calendarData['id'])
+			->setType(Extension::CALENDAR)
+			->setAuthor($currentUser);
+
+		foreach ($remove as $principal) {
+			// principal:principals/users/test
+			$parts = explode(':', $principal, 2);
+			if ($parts[0] !== 'principal') {
+				continue;
+			}
+			$principal = explode('/', $parts[1]);
+
+			if ($principal[1] === 'users') {
+				$this->triggerActivityUser(
+					$principal[2],
+					$event,
+					$calendarData,
+					Extension::SUBJECT_UNSHARE_USER,
+					Extension::SUBJECT_DELETE . '_self'
+				);
+
+				if ($owner !== $principal[2]) {
+					$parameters = [
+						$principal[2],
+						$calendarData['{DAV:}displayname'],
+					];
+
+					if ($owner === $event->getAuthor()) {
+						$subject = Extension::SUBJECT_UNSHARE_USER . '_you';
+					} else if ($principal[2] === $event->getAuthor()) {
+						$subject = Extension::SUBJECT_UNSHARE_USER . '_self';
+					} else {
+						$event->setAffectedUser($event->getAuthor())
+							->setSubject(Extension::SUBJECT_UNSHARE_USER . '_you', $parameters);
+						$this->activityManager->publish($event);
+
+						$subject = Extension::SUBJECT_UNSHARE_USER . '_by';
+						$parameters[] = $event->getAuthor();
+					}
+
+					$event->setAffectedUser($owner)
+						->setSubject($subject, $parameters);
+					$this->activityManager->publish($event);
+				}
+			} else if ($principal[1] === 'groups') {
+				$this->triggerActivityGroup($principal[2], $event, $calendarData, Extension::SUBJECT_UNSHARE_USER);
+
+				$parameters = [
+					$principal[2],
+					$calendarData['{DAV:}displayname'],
+				];
+
+				if ($owner === $event->getAuthor()) {
+					$subject = Extension::SUBJECT_UNSHARE_GROUP . '_you';
+				} else {
+					$event->setAffectedUser($event->getAuthor())
+						->setSubject(Extension::SUBJECT_UNSHARE_GROUP . '_you', $parameters);
+					$this->activityManager->publish($event);
+
+					$subject = Extension::SUBJECT_UNSHARE_GROUP . '_by';
+					$parameters[] = $event->getAuthor();
+				}
+
+				$event->setAffectedUser($owner)
+					->setSubject($subject, $parameters);
+				$this->activityManager->publish($event);
+			}
+		}
+
+		foreach ($add as $share) {
+			if ($this->isAlreadyShared($share['href'], $shares)) {
+				continue;
+			}
+
+			// principal:principals/users/test
+			$parts = explode(':', $share['href'], 2);
+			if ($parts[0] !== 'principal') {
+				continue;
+			}
+			$principal = explode('/', $parts[1]);
+
+			if ($principal[1] === 'users') {
+				$this->triggerActivityUser($principal[2], $event, $calendarData, Extension::SUBJECT_SHARE_USER);
+
+				if ($owner !== $principal[2]) {
+					$parameters = [
+						$principal[2],
+						$calendarData['{DAV:}displayname'],
+					];
+
+					if ($owner === $event->getAuthor()) {
+						$subject = Extension::SUBJECT_SHARE_USER . '_you';
+					} else {
+						$event->setAffectedUser($event->getAuthor())
+							->setSubject(Extension::SUBJECT_SHARE_USER . '_you', $parameters);
+						$this->activityManager->publish($event);
+
+						$subject = Extension::SUBJECT_SHARE_USER . '_by';
+						$parameters[] = $event->getAuthor();
+					}
+
+					$event->setAffectedUser($owner)
+						->setSubject($subject, $parameters);
+					$this->activityManager->publish($event);
+				}
+			} else if ($principal[1] === 'groups') {
+				$this->triggerActivityGroup($principal[2], $event, $calendarData, Extension::SUBJECT_SHARE_USER);
+
+				$parameters = [
+					$principal[2],
+					$calendarData['{DAV:}displayname'],
+				];
+
+				if ($owner === $event->getAuthor()) {
+					$subject = Extension::SUBJECT_SHARE_GROUP . '_you';
+				} else {
+					$event->setAffectedUser($event->getAuthor())
+						->setSubject(Extension::SUBJECT_SHARE_GROUP . '_you', $parameters);
+					$this->activityManager->publish($event);
+
+					$subject = Extension::SUBJECT_SHARE_GROUP . '_by';
+					$parameters[] = $event->getAuthor();
+				}
+
+				$event->setAffectedUser($owner)
+					->setSubject($subject, $parameters);
+				$this->activityManager->publish($event);
+			}
+		}
+	}
+
+	/**
+	 * Checks if a calendar is already shared with a principal
+	 *
+	 * @param string $principal
+	 * @param array[] $shares
+	 * @return bool
+	 */
+	protected function isAlreadyShared($principal, $shares) {
+		foreach ($shares as $share) {
+			if ($principal === $share['href']) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * Creates the given activity for all members of the given group
+	 *
+	 * @param string $gid
+	 * @param IEvent $event
+	 * @param array $properties
+	 * @param string $subject
+	 */
+	protected function triggerActivityGroup($gid, IEvent $event, array $properties, $subject) {
+		$group = $this->groupManager->get($gid);
+
+		if ($group instanceof IGroup) {
+			foreach ($group->getUsers() as $user) {
+				// Exclude current user
+				if ($user->getUID() !== $event->getAuthor()) {
+					$this->triggerActivityUser($user->getUID(), $event, $properties, $subject);
+				}
+			}
+		}
+	}
+
+	/**
+	 * Creates the given activity for the given user
+	 *
+	 * @param string $user
+	 * @param IEvent $event
+	 * @param array $properties
+	 * @param string $subject
+	 * @param string $subjectSelf
+	 */
+	protected function triggerActivityUser($user, IEvent $event, array $properties, $subject, $subjectSelf = '') {
+		$event->setAffectedUser($user)
+			->setSubject(
+				$user === $event->getAuthor() && $subjectSelf ? $subjectSelf : $subject,
+				[
+					$event->getAuthor(),
+					$properties['{DAV:}displayname'],
+				]
+			);
+
+		$this->activityManager->publish($event);
+	}
+
+	/**
+	 * Creates activities when a calendar object was created/updated/deleted
+	 *
+	 * @param string $action
+	 * @param array $calendarData
+	 * @param array $shares
+	 * @param array $objectData
+	 */
+	public function onTouchCalendarObject($action, array $calendarData, array $shares, array $objectData) {
+		if (!isset($calendarData['principaluri'])) {
+			return;
+		}
+
+		$principal = explode('/', $calendarData['principaluri']);
+		$owner = $principal[2];
+
+		$currentUser = $this->userSession->getUser();
+		if ($currentUser instanceof IUser) {
+			$currentUser = $currentUser->getUID();
+		} else {
+			$currentUser = $owner;
+		}
+
+		$object = $this->getObjectNameAndType($objectData);
+		$action = $action . '_' . $object['type'];
+
+		if ($object['type'] === 'todo' && strpos($action, Extension::SUBJECT_OBJECT_UPDATE) === 0 && $object['status'] === 'COMPLETED') {
+			$action .= '_completed';
+		} else if ($object['type'] === 'todo' && strpos($action, Extension::SUBJECT_OBJECT_UPDATE) === 0 && $object['status'] === 'NEEDS-ACTION') {
+			$action .= '_needs_action';
+		}
+
+		$event = $this->activityManager->generateEvent();
+		$event->setApp('dav')
+			->setObject(Extension::CALENDAR, $calendarData['id'])
+			->setType($object['type'] === 'event' ? Extension::CALENDAR_EVENT : Extension::CALENDAR_TODO)
+			->setAuthor($currentUser);
+
+		$users = $this->getUsersForShares($shares);
+		$users[] = $owner;
+
+		foreach ($users as $user) {
+			$event->setAffectedUser($user)
+				->setSubject(
+					$user === $currentUser ? $action . '_self' : $action,
+					[
+						$currentUser,
+						$calendarData['{DAV:}displayname'],
+						$object['name'],
+					]
+				);
+			$this->activityManager->publish($event);
+		}
+	}
+
+	/**
+	 * @param array $objectData
+	 * @return string[]|bool
+	 */
+	protected function getObjectNameAndType(array $objectData) {
+		$vObject = Reader::read($objectData['calendardata']);
+		$component = $componentType = null;
+		foreach($vObject->getComponents() as $component) {
+			if (in_array($component->name, ['VEVENT', 'VTODO'])) {
+				$componentType = $component->name;
+				break;
+			}
+		}
+
+		if (!$componentType) {
+			// Calendar objects must have a VEVENT or VTODO component
+			return false;
+		}
+
+		if ($componentType === 'VEVENT') {
+			return ['name' => (string) $component->SUMMARY, 'type' => 'event'];
+		}
+		return ['name' => (string) $component->SUMMARY, 'type' => 'todo', 'status' => (string) $component->STATUS];
+	}
+
+	/**
+	 * Get all users that have access to a given calendar
+	 *
+	 * @param array $shares
+	 * @return string[]
+	 */
+	protected function getUsersForShares(array $shares) {
+		$users = $groups = [];
+		foreach ($shares as $share) {
+			$prinical = explode('/', $share['{http://owncloud.org/ns}principal']);
+			if ($prinical[1] === 'users') {
+				$users[] = $prinical[2];
+			} else if ($prinical[1] === 'groups') {
+				$groups[] = $prinical[2];
+			}
+		}
+
+		if (!empty($groups)) {
+			foreach ($groups as $gid) {
+				$group = $this->groupManager->get($gid);
+				if ($group instanceof IGroup) {
+					foreach ($group->getUsers() as $user) {
+						$users[] = $user->getUID();
+					}
+				}
+			}
+		}
+
+		return array_unique($users);
+	}
+}
diff --git a/apps/dav/lib/CalDAV/Activity/Extension.php b/apps/dav/lib/CalDAV/Activity/Extension.php
new file mode 100644
index 0000000000000..29222b90ce8d0
--- /dev/null
+++ b/apps/dav/lib/CalDAV/Activity/Extension.php
@@ -0,0 +1,378 @@
+<?php
+/**
+ * @copyright Copyright (c) 2016 Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\DAV\CalDAV\Activity;
+
+use OCP\Activity\IExtension;
+use OCP\IURLGenerator;
+use OCP\L10N\IFactory;
+
+class Extension implements IExtension {
+	const APP = 'dav';
+	/**
+	 * Filter with all sharing related activities
+	 */
+	const CALENDAR = 'calendar';
+	const CALENDAR_EVENT = 'calendar_event';
+	const CALENDAR_TODO = 'calendar_todo';
+
+	const SUBJECT_ADD = 'calendar_add';
+	const SUBJECT_UPDATE = 'calendar_update';
+	const SUBJECT_DELETE = 'calendar_delete';
+	const SUBJECT_SHARE_USER = 'calendar_user_share';
+	const SUBJECT_SHARE_GROUP = 'calendar_group_share';
+	const SUBJECT_UNSHARE_USER = 'calendar_user_unshare';
+	const SUBJECT_UNSHARE_GROUP = 'calendar_group_unshare';
+
+	const SUBJECT_OBJECT_ADD = 'object_add';
+	const SUBJECT_OBJECT_UPDATE = 'object_update';
+	const SUBJECT_OBJECT_DELETE = 'object_delete';
+
+	/** @var IFactory */
+	protected $languageFactory;
+
+	/** @var IURLGenerator */
+	protected $URLGenerator;
+
+	/**
+	 * @param IFactory $languageFactory
+	 * @param IURLGenerator $URLGenerator
+	 */
+	public function __construct(IFactory $languageFactory, IURLGenerator $URLGenerator) {
+		$this->languageFactory = $languageFactory;
+		$this->URLGenerator = $URLGenerator;
+	}
+
+	protected function getL10N($languageCode = null) {
+		return $this->languageFactory->get(self::APP, $languageCode);
+	}
+
+	/**
+	 * The extension can return an array of additional notification types.
+	 * If no additional types are to be added false is to be returned
+	 *
+	 * @param string $languageCode
+	 * @return array|false
+	 */
+	public function getNotificationTypes($languageCode) {
+		$l = $this->getL10N($languageCode);
+
+		return array(
+			self::CALENDAR => (string) $l->t('A <strong>calendar</strong> was modified'),
+			self::CALENDAR_EVENT => (string) $l->t('A calendar <strong>event</strong> was modified'),
+			self::CALENDAR_TODO => (string) $l->t('A calendar <strong>todo</strong> was modified'),
+		);
+	}
+
+	/**
+	 * For a given method additional types to be displayed in the settings can be returned.
+	 * In case no additional types are to be added false is to be returned.
+	 *
+	 * @param string $method
+	 * @return array|false
+	 */
+	public function getDefaultTypes($method) {
+		$defaultTypes = [];
+		if ($method === self::METHOD_STREAM) {
+			$defaultTypes[] = self::CALENDAR;
+			$defaultTypes[] = self::CALENDAR_EVENT;
+			$defaultTypes[] = self::CALENDAR_TODO;
+		}
+
+		return $defaultTypes;
+	}
+
+	/**
+	 * A string naming the css class for the icon to be used can be returned.
+	 * If no icon is known for the given type false is to be returned.
+	 *
+	 * @param string $type
+	 * @return string|false
+	 */
+	public function getTypeIcon($type) {
+		switch ($type) {
+			case self::CALENDAR:
+			case self::CALENDAR_EVENT:
+				return 'icon-calendar-dark';
+			case self::CALENDAR_TODO:
+				return 'icon-checkmark';
+		}
+
+		return false;
+	}
+
+	/**
+	 * The extension can translate a given message to the requested languages.
+	 * If no translation is available false is to be returned.
+	 *
+	 * @param string $app
+	 * @param string $text
+	 * @param array $params
+	 * @param boolean $stripPath
+	 * @param boolean $highlightParams
+	 * @param string $languageCode
+	 * @return string|false
+	 */
+	public function translate($app, $text, $params, $stripPath, $highlightParams, $languageCode) {
+		if ($app !== self::APP) {
+			return false;
+		}
+
+		$l = $this->getL10N($languageCode);
+
+		switch ($text) {
+			case self::SUBJECT_ADD:
+				return (string) $l->t('%1$s created calendar %2$s', $params);
+			case self::SUBJECT_ADD . '_self':
+				return (string) $l->t('You created calendar %2$s', $params);
+			case self::SUBJECT_DELETE:
+				return (string) $l->t('%1$s deleted calendar %2$s', $params);
+			case self::SUBJECT_DELETE . '_self':
+				return (string) $l->t('You deleted calendar %2$s', $params);
+			case self::SUBJECT_UPDATE:
+				return (string) $l->t('%1$s updated calendar %2$s', $params);
+			case self::SUBJECT_UPDATE . '_self':
+				return (string) $l->t('You updated calendar %2$s', $params);
+
+			case self::SUBJECT_SHARE_USER:
+				return (string) $l->t('%1$s shared calendar %2$s with you', $params);
+			case self::SUBJECT_SHARE_USER . '_you':
+				return (string) $l->t('You shared calendar %2$s with %1$s', $params);
+			case self::SUBJECT_SHARE_USER . '_by':
+				return (string) $l->t('%3$s shared calendar %2$s with %1$s', $params);
+			case self::SUBJECT_UNSHARE_USER:
+				return (string) $l->t('%1$s unshared calendar %2$s from you', $params);
+			case self::SUBJECT_UNSHARE_USER . '_you':
+				return (string) $l->t('You unshared calendar %2$s from %1$s', $params);
+			case self::SUBJECT_UNSHARE_USER . '_by':
+				return (string) $l->t('%3$s unshared calendar %2$s from %1$s', $params);
+			case self::SUBJECT_UNSHARE_USER . '_self':
+				return (string) $l->t('%1$s unshared calendar %2$s from themselves', $params);
+
+			case self::SUBJECT_SHARE_GROUP . '_you':
+				return (string) $l->t('You shared calendar %2$s with group %1$s', $params);
+			case self::SUBJECT_SHARE_GROUP . '_by':
+				return (string) $l->t('%3$s shared calendar %2$s with group %1$s', $params);
+			case self::SUBJECT_UNSHARE_GROUP . '_you':
+				return (string) $l->t('You unshared calendar %2$s from group %1$s', $params);
+			case self::SUBJECT_UNSHARE_GROUP . '_by':
+				return (string) $l->t('%3$s unshared calendar %2$s from group %1$s', $params);
+
+			case self::SUBJECT_OBJECT_ADD . '_event':
+				return (string) $l->t('%1$s created event %3$s in calendar %2$s', $params);
+			case self::SUBJECT_OBJECT_ADD . '_event_self':
+				return (string) $l->t('You created event %3$s in calendar %2$s', $params);
+			case self::SUBJECT_OBJECT_DELETE . '_event':
+				return (string) $l->t('%1$s deleted event %3$s from calendar %2$s', $params);
+			case self::SUBJECT_OBJECT_DELETE . '_event_self':
+				return (string) $l->t('You deleted event %3$s from calendar %2$s', $params);
+			case self::SUBJECT_OBJECT_UPDATE . '_event':
+				return (string) $l->t('%1$s updated event %3$s in calendar %2$s', $params);
+			case self::SUBJECT_OBJECT_UPDATE . '_event_self':
+				return (string) $l->t('You updated event %3$s in calendar %2$s', $params);
+
+			case self::SUBJECT_OBJECT_ADD . '_todo':
+				return (string) $l->t('%1$s created todo %3$s in list %2$s', $params);
+			case self::SUBJECT_OBJECT_ADD . '_todo_self':
+				return (string) $l->t('You created todo %3$s in list %2$s', $params);
+			case self::SUBJECT_OBJECT_DELETE . '_todo':
+				return (string) $l->t('%1$s deleted todo %3$s from list %2$s', $params);
+			case self::SUBJECT_OBJECT_DELETE . '_todo_self':
+				return (string) $l->t('You deleted todo %3$s from list %2$s', $params);
+			case self::SUBJECT_OBJECT_UPDATE . '_todo':
+				return (string) $l->t('%1$s updated todo %3$s in list %2$s', $params);
+			case self::SUBJECT_OBJECT_UPDATE . '_todo_self':
+				return (string) $l->t('You updated todo %3$s in list %2$s', $params);
+
+			case self::SUBJECT_OBJECT_UPDATE . '_todo_completed':
+				return (string) $l->t('%1$s solved todo %3$s in list %2$s', $params);
+			case self::SUBJECT_OBJECT_UPDATE . '_todo_completed_self':
+				return (string) $l->t('You solved todo %3$s in list %2$s', $params);
+			case self::SUBJECT_OBJECT_UPDATE . '_todo_needs_action':
+				return (string) $l->t('%1$s reopened todo %3$s in list %2$s', $params);
+			case self::SUBJECT_OBJECT_UPDATE . '_todo_needs_action_self':
+				return (string) $l->t('You reopened todo %3$s in list %2$s', $params);
+
+		}
+
+		return false;
+	}
+
+	/**
+	 * The extension can define the type of parameters for translation
+	 *
+	 * Currently known types are:
+	 * * file		=> will strip away the path of the file and add a tooltip with it
+	 * * username	=> will add the avatar of the user
+	 *
+	 * @param string $app
+	 * @param string $text
+	 * @return array|false
+	 */
+	public function getSpecialParameterList($app, $text) {
+		if ($app === self::APP) {
+			switch ($text) {
+				case self::SUBJECT_ADD:
+				case self::SUBJECT_ADD . '_self':
+				case self::SUBJECT_DELETE:
+				case self::SUBJECT_DELETE . '_self':
+				case self::SUBJECT_UPDATE:
+				case self::SUBJECT_UPDATE . '_self':
+				case self::SUBJECT_SHARE_USER:
+				case self::SUBJECT_SHARE_USER . '_you':
+				case self::SUBJECT_UNSHARE_USER:
+				case self::SUBJECT_UNSHARE_USER . '_you':
+				case self::SUBJECT_UNSHARE_USER . '_self':
+					return [
+						0 => 'username',
+						//1 => 'calendar',
+					];
+				case self::SUBJECT_SHARE_USER . '_by':
+				case self::SUBJECT_UNSHARE_USER . '_by':
+					return [
+						0 => 'username',
+						//1 => 'calendar',
+						2 => 'username',
+					];
+				case self::SUBJECT_SHARE_GROUP . '_you':
+				case self::SUBJECT_UNSHARE_GROUP . '_you':
+					return [
+						//0 => 'group',
+						//1 => 'calendar',
+					];
+				case self::SUBJECT_SHARE_GROUP . '_by':
+				case self::SUBJECT_UNSHARE_GROUP . '_by':
+					return [
+						//0 => 'group',
+						//1 => 'calendar',
+						2 => 'username',
+					];
+
+				case self::SUBJECT_OBJECT_ADD . '_event':
+				case self::SUBJECT_OBJECT_ADD . '_event_self':
+				case self::SUBJECT_OBJECT_DELETE . '_event':
+				case self::SUBJECT_OBJECT_DELETE . '_event_self':
+				case self::SUBJECT_OBJECT_UPDATE . '_event':
+				case self::SUBJECT_OBJECT_UPDATE . '_event_self':
+
+				case self::SUBJECT_OBJECT_ADD . '_todo':
+				case self::SUBJECT_OBJECT_ADD . '_todo_self':
+				case self::SUBJECT_OBJECT_DELETE . '_todo':
+				case self::SUBJECT_OBJECT_DELETE . '_todo_self':
+				case self::SUBJECT_OBJECT_UPDATE . '_todo':
+				case self::SUBJECT_OBJECT_UPDATE . '_todo_self':
+
+				case self::SUBJECT_OBJECT_UPDATE . '_todo_completed':
+				case self::SUBJECT_OBJECT_UPDATE . '_todo_completed_self':
+				case self::SUBJECT_OBJECT_UPDATE . '_todo_needs_action':
+				case self::SUBJECT_OBJECT_UPDATE . '_todo_needs_action_self':
+					return [
+						0 => 'username',
+						//1 => 'calendar',
+						//2 => 'object',
+					];
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * The extension can define the parameter grouping by returning the index as integer.
+	 * In case no grouping is required false is to be returned.
+	 *
+	 * @param array $activity
+	 * @return integer|false
+	 */
+	public function getGroupParameter($activity) {
+		return false;
+	}
+
+	/**
+	 * The extension can define additional navigation entries. The array returned has to contain two keys 'top'
+	 * and 'apps' which hold arrays with the relevant entries.
+	 * If no further entries are to be added false is no be returned.
+	 *
+	 * @return array|false
+	 */
+	public function getNavigation() {
+		$l = $this->getL10N();
+		return [
+			'apps' => [
+				self::CALENDAR => [
+					'id' => self::CALENDAR,
+					'icon' => 'icon-calendar-dark',
+					'name' => (string) $l->t('Calendar'),
+					'url' => $this->URLGenerator->linkToRoute('activity.Activities.showList', ['filter' => self::CALENDAR]),
+				],
+				self::CALENDAR_TODO => [
+					'id' => self::CALENDAR_TODO,
+					'icon' => 'icon-checkmark',
+					'name' => (string) $l->t('Todos'),
+					'url' => $this->URLGenerator->linkToRoute('activity.Activities.showList', ['filter' => self::CALENDAR_TODO]),
+				],
+			],
+			'top' => [],
+		];
+	}
+
+	/**
+	 * The extension can check if a custom filter (given by a query string like filter=abc) is valid or not.
+	 *
+	 * @param string $filterValue
+	 * @return boolean
+	 */
+	public function isFilterValid($filterValue) {
+		return in_array($filterValue, [self::CALENDAR, self::CALENDAR_TODO]);
+	}
+
+	/**
+	 * The extension can filter the types based on the filter if required.
+	 * In case no filter is to be applied false is to be returned unchanged.
+	 *
+	 * @param array $types
+	 * @param string $filter
+	 * @return array|false
+	 */
+	public function filterNotificationTypes($types, $filter) {
+		switch ($filter) {
+			case self::CALENDAR:
+				return array_intersect([self::CALENDAR, self::CALENDAR_EVENT], $types);
+			case self::CALENDAR_TODO:
+				return array_intersect([self::CALENDAR_TODO], $types);
+		}
+		return false;
+	}
+
+	/**
+	 * For a given filter the extension can specify the sql query conditions including parameters for that query.
+	 * In case the extension does not know the filter false is to be returned.
+	 * The query condition and the parameters are to be returned as array with two elements.
+	 * E.g. return array('`app` = ? and `message` like ?', array('mail', 'ownCloud%'));
+	 *
+	 * @param string $filter
+	 * @return array|false
+	 */
+	public function getQueryForFilter($filter) {
+		return false;
+	}
+
+}
diff --git a/apps/dav/lib/CalDAV/CalDavBackend.php b/apps/dav/lib/CalDAV/CalDavBackend.php
index 07b61285eca26..fb608c2009de4 100644
--- a/apps/dav/lib/CalDAV/CalDavBackend.php
+++ b/apps/dav/lib/CalDAV/CalDavBackend.php
@@ -29,7 +29,6 @@
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCA\DAV\Connector\Sabre\Principal;
 use OCA\DAV\DAV\Sharing\Backend;
-use OCP\IConfig;
 use OCP\IDBConnection;
 use OCP\IUser;
 use OCP\IUserManager;
@@ -49,6 +48,8 @@
 use Sabre\VObject\DateTimeParser;
 use Sabre\VObject\Reader;
 use Sabre\VObject\Recur\EventIterator;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\EventDispatcher\GenericEvent;
 
 /**
  * Class CalDavBackend
@@ -124,33 +125,33 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 
 	/** @var IUserManager */
 	private $userManager;
-	
-	/** @var IConfig */
-	private $config;
 
 	/** @var ISecureRandom */
 	private $random;
 
+	/** @var EventDispatcherInterface */
+	private $dispatcher;
+
 	/**
 	 * CalDavBackend constructor.
 	 *
 	 * @param IDBConnection $db
 	 * @param Principal $principalBackend
 	 * @param IUserManager $userManager
-	 * @param IConfig $config
 	 * @param ISecureRandom $random
+	 * @param EventDispatcherInterface $dispatcher
 	 */
 	public function __construct(IDBConnection $db,
 								Principal $principalBackend,
 								IUserManager $userManager,
-								IConfig $config,
-								ISecureRandom $random) {
+								ISecureRandom $random,
+								EventDispatcherInterface $dispatcher) {
 		$this->db = $db;
 		$this->principalBackend = $principalBackend;
 		$this->userManager = $userManager;
 		$this->sharingBackend = new Backend($this->db, $principalBackend, 'calendar');
-		$this->config = $config;
 		$this->random = $random;
+		$this->dispatcher = $dispatcher;
 	}
 
 	/**
@@ -613,7 +614,16 @@ function createCalendar($principalUri, $calendarUri, array $properties) {
 			$query->setValue($column, $query->createNamedParameter($value));
 		}
 		$query->execute();
-		return $query->getLastInsertId();
+		$calendarId = $query->getLastInsertId();
+
+		$this->dispatcher->dispatch('\OCA\DAV\CalDAV\CalDavBackend::createCalendar', new GenericEvent(
+			'\OCA\DAV\CalDAV\CalDavBackend::createCalendar',
+			[
+				'calendarId' => $calendarId,
+				'calendarData' => $this->getCalendarById($calendarId),
+		]));
+
+		return $calendarId;
 	}
 
 	/**
@@ -661,6 +671,15 @@ function updateCalendar($calendarId, PropPatch $propPatch) {
 
 			$this->addChange($calendarId, "", 2);
 
+			$this->dispatcher->dispatch('\OCA\DAV\CalDAV\CalDavBackend::updateCalendar', new GenericEvent(
+				'\OCA\DAV\CalDAV\CalDavBackend::updateCalendar',
+				[
+					'calendarId' => $calendarId,
+					'calendarData' => $this->getCalendarById($calendarId),
+					'shares' => $this->getShares($calendarId),
+					'propertyMutations' => $mutations,
+			]));
+
 			return true;
 		});
 	}
@@ -672,6 +691,14 @@ function updateCalendar($calendarId, PropPatch $propPatch) {
 	 * @return void
 	 */
 	function deleteCalendar($calendarId) {
+		$this->dispatcher->dispatch('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendar', new GenericEvent(
+			'\OCA\DAV\CalDAV\CalDavBackend::deleteCalendar',
+			[
+				'calendarId' => $calendarId,
+				'calendarData' => $this->getCalendarById($calendarId),
+				'shares' => $this->getShares($calendarId),
+		]));
+
 		$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendarobjects` WHERE `calendarid` = ?');
 		$stmt->execute([$calendarId]);
 
@@ -876,6 +903,15 @@ function createCalendarObject($calendarId, $objectUri, $calendarData) {
 			])
 			->execute();
 
+		$this->dispatcher->dispatch('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject', new GenericEvent(
+			'\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject',
+			[
+				'calendarId' => $calendarId,
+				'calendarData' => $this->getCalendarById($calendarId),
+				'shares' => $this->getShares($calendarId),
+				'objectData' => $this->getCalendarObject($calendarId, $objectUri),
+			]
+		));
 		$this->addChange($calendarId, $objectUri, 1);
 
 		return '"' . $extraData['etag'] . '"';
@@ -917,6 +953,18 @@ function updateCalendarObject($calendarId, $objectUri, $calendarData) {
 			->andWhere($query->expr()->eq('uri', $query->createNamedParameter($objectUri)))
 			->execute();
 
+		$data = $this->getCalendarObject($calendarId, $objectUri);
+		if (is_array($data)) {
+			$this->dispatcher->dispatch('\OCA\DAV\CalDAV\CalDavBackend::updateCalendarObject', new GenericEvent(
+				'\OCA\DAV\CalDAV\CalDavBackend::updateCalendarObject',
+				[
+					'calendarId' => $calendarId,
+					'calendarData' => $this->getCalendarById($calendarId),
+					'shares' => $this->getShares($calendarId),
+					'objectData' => $data,
+				]
+			));
+		}
 		$this->addChange($calendarId, $objectUri, 2);
 
 		return '"' . $extraData['etag'] . '"';
@@ -949,6 +997,19 @@ public function setClassification($calendarObjectId, $classification) {
 	 * @return void
 	 */
 	function deleteCalendarObject($calendarId, $objectUri) {
+		$data = $this->getCalendarObject($calendarId, $objectUri);
+		if (is_array($data)) {
+			$this->dispatcher->dispatch('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject', new GenericEvent(
+				'\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject',
+				[
+					'calendarId' => $calendarId,
+					'calendarData' => $this->getCalendarById($calendarId),
+					'shares' => $this->getShares($calendarId),
+					'objectData' => $data,
+				]
+			));
+		}
+
 		$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendarobjects` WHERE `calendarid` = ? AND `uri` = ?');
 		$stmt->execute([$calendarId, $objectUri]);
 
@@ -1648,6 +1709,16 @@ private function readBlob($cardData) {
 	 * @param array $remove
 	 */
 	public function updateShares($shareable, $add, $remove) {
+		$calendarId = $shareable->getResourceId();
+		$this->dispatcher->dispatch('\OCA\DAV\CalDAV\CalDavBackend::updateShares', new GenericEvent(
+			'\OCA\DAV\CalDAV\CalDavBackend::updateShares',
+			[
+				'calendarId' => $calendarId,
+				'calendarData' => $this->getCalendarById($calendarId),
+				'shares' => $this->getShares($calendarId),
+				'add' => $add,
+				'remove' => $remove,
+			]));
 		$this->sharingBackend->updateShares($shareable, $add, $remove);
 	}
 
diff --git a/apps/dav/lib/Command/CreateCalendar.php b/apps/dav/lib/Command/CreateCalendar.php
index da1f706a8b810..24990352fabe2 100644
--- a/apps/dav/lib/Command/CreateCalendar.php
+++ b/apps/dav/lib/Command/CreateCalendar.php
@@ -75,11 +75,11 @@ protected function execute(InputInterface $input, OutputInterface $output) {
 			$this->userManager,
 			$this->groupManager
 		);
-		$config = \OC::$server->getConfig();
 		$random = \OC::$server->getSecureRandom();
+		$dispatcher = \OC::$server->getEventDispatcher();
 
 		$name = $input->getArgument('name');
-		$caldav = new CalDavBackend($this->dbConnection, $principalBackend, $this->userManager, $config, $random);
+		$caldav = new CalDavBackend($this->dbConnection, $principalBackend, $this->userManager, $random, $dispatcher);
 		$caldav->createCalendar("principals/users/$user", $name, []);
 	}
 }
diff --git a/apps/dav/lib/RootCollection.php b/apps/dav/lib/RootCollection.php
index 4c76dc30c3fcc..478f0929c2014 100644
--- a/apps/dav/lib/RootCollection.php
+++ b/apps/dav/lib/RootCollection.php
@@ -62,7 +62,7 @@ public function __construct() {
 		$systemPrincipals->disableListing = $disableListing;
 		$filesCollection = new Files\RootCollection($userPrincipalBackend, 'principals/users');
 		$filesCollection->disableListing = $disableListing;
-		$caldavBackend = new CalDavBackend($db, $userPrincipalBackend, $userManager, $config, $random);
+		$caldavBackend = new CalDavBackend($db, $userPrincipalBackend, $userManager, $random, $dispatcher);
 		$calendarRoot = new CalendarRoot($userPrincipalBackend, $caldavBackend, 'principals/users');
 		$calendarRoot->disableListing = $disableListing;
 		$publicCalendarRoot = new PublicCalendarRoot($caldavBackend);
diff --git a/apps/dav/tests/unit/CalDAV/AbstractCalDavBackendTest.php b/apps/dav/tests/unit/CalDAV/AbstractCalDavBackendTest.php
index 2559ecbbf89e2..d15be72c77be1 100644
--- a/apps/dav/tests/unit/CalDAV/AbstractCalDavBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/AbstractCalDavBackendTest.php
@@ -22,18 +22,12 @@
 
 namespace OCA\DAV\Tests\unit\CalDAV;
 
-use DateTime;
-use DateTimeZone;
 use OCA\DAV\CalDAV\CalDavBackend;
-use OCA\DAV\CalDAV\Calendar;
 use OCA\DAV\Connector\Sabre\Principal;
-use OCP\IL10N;
-use OCP\IConfig;
+use OCP\IUserManager;
 use OCP\Security\ISecureRandom;
 use Sabre\CalDAV\Xml\Property\SupportedCalendarComponentSet;
-use Sabre\DAV\PropPatch;
-use Sabre\DAV\Xml\Property\Href;
-use Sabre\DAVACL\IACL;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Test\TestCase;
 
 /**
@@ -50,12 +44,10 @@ abstract class AbstractCalDavBackendTest extends TestCase {
 
 	/** @var Principal | \PHPUnit_Framework_MockObject_MockObject */
 	protected $principal;
-
-	/** @var \OCP\IUserManager|\PHPUnit_Framework_MockObject_MockObject */
+	/** @var IUserManager|\PHPUnit_Framework_MockObject_MockObject */
 	protected $userManager;
-	
-	/** var OCP\IConfig */
-	protected $config;
+	/** @var EventDispatcherInterface|\PHPUnit_Framework_MockObject_MockObject */
+	protected $dispatcher;
 
 	/** @var ISecureRandom */
 	private $random;
@@ -67,9 +59,8 @@ abstract class AbstractCalDavBackendTest extends TestCase {
 	public function setUp() {
 		parent::setUp();
 
-		$this->userManager = $this->getMockBuilder('OCP\IUserManager')
-			->disableOriginalConstructor()
-			->getMock();
+		$this->userManager = $this->createMock(IUserManager::class);
+		$this->dispatcher = $this->createMock(EventDispatcherInterface::class);
 		$this->principal = $this->getMockBuilder('OCA\DAV\Connector\Sabre\Principal')
 			->disableOriginalConstructor()
 			->setMethods(['getPrincipalByPath', 'getGroupMembership'])
@@ -83,21 +74,28 @@ public function setUp() {
 			->willReturn([self::UNIT_TEST_GROUP]);
 
 		$db = \OC::$server->getDatabaseConnection();
-		$this->config = \OC::$server->getConfig();
 		$this->random = \OC::$server->getSecureRandom();
-		$this->backend = new CalDavBackend($db, $this->principal, $this->userManager, $this->config, $this->random);
-		$this->tearDown();
+		$this->backend = new CalDavBackend($db, $this->principal, $this->userManager, $this->random, $this->dispatcher);
+
+		$this->cleanUpBackend();
 	}
 
 	public function tearDown() {
+		$this->cleanUpBackend();
 		parent::tearDown();
+	}
 
+	public function cleanUpBackend() {
 		if (is_null($this->backend)) {
 			return;
 		}
-		$books = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
-		foreach ($books as $book) {
-			$this->backend->deleteCalendar($book['id']);
+		$calendars = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
+		foreach ($calendars as $calendar) {
+			$this->dispatcher->expects($this->at(0))
+				->method('dispatch')
+				->with('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendar');
+
+			$this->backend->deleteCalendar($calendar['id']);
 		}
 		$subscriptions = $this->backend->getSubscriptionsForUser(self::UNIT_TEST_USER);
 		foreach ($subscriptions as $subscription) {
@@ -106,6 +104,10 @@ public function tearDown() {
 	}
 
 	protected function createTestCalendar() {
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendar');
+
 		$this->backend->createCalendar(self::UNIT_TEST_USER, 'Example', [
 			'{http://apple.com/ns/ical/}calendar-color' => '#1C4587FF'
 		]);
@@ -143,6 +145,11 @@ protected function createEvent($calendarId, $start = '20130912T130000Z', $end =
 END:VCALENDAR
 EOD;
 		$uri0 = $this->getUniqueID('event');
+
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject');
+
 		$this->backend->createCalendarObject($calendarId, $uri0, $calData);
 
 		return $uri0;
diff --git a/apps/dav/tests/unit/CalDAV/Activity/BackendTest.php b/apps/dav/tests/unit/CalDAV/Activity/BackendTest.php
new file mode 100644
index 0000000000000..3585d69bad32c
--- /dev/null
+++ b/apps/dav/tests/unit/CalDAV/Activity/BackendTest.php
@@ -0,0 +1,332 @@
+<?php
+/**
+ * @copyright Copyright (c) 2016 Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\DAV\Tests\unit\CalDAV\Activity;
+
+use OCA\DAV\CalDAV\Activity\Backend;
+use OCA\DAV\CalDAV\Activity\Extension;
+use OCP\Activity\IEvent;
+use OCP\Activity\IManager;
+use OCP\IGroup;
+use OCP\IGroupManager;
+use OCP\IUser;
+use OCP\IUserSession;
+use Test\TestCase;
+
+class BackendTest extends TestCase {
+
+	/** @var IManager|\PHPUnit_Framework_MockObject_MockObject */
+	protected $activityManager;
+
+	/** @var IGroupManager|\PHPUnit_Framework_MockObject_MockObject */
+	protected $groupManager;
+
+	/** @var IUserSession|\PHPUnit_Framework_MockObject_MockObject */
+	protected $userSession;
+
+	protected function setUp() {
+		parent::setUp();
+		$this->activityManager = $this->createMock(IManager::class);
+		$this->groupManager = $this->createMock(IGroupManager::class);
+		$this->userSession = $this->createMock(IUserSession::class);
+	}
+
+	/**
+	 * @param array $methods
+	 * @return Backend|\PHPUnit_Framework_MockObject_MockObject
+	 */
+	protected function getBackend(array $methods = []) {
+		if (empty($methods)) {
+			return new Backend(
+				$this->activityManager,
+				$this->groupManager,
+				$this->userSession
+			);
+		} else {
+			return $this->getMockBuilder(Backend::class)
+				->setConstructorArgs([
+					$this->activityManager,
+					$this->groupManager,
+					$this->userSession,
+				])
+				->setMethods($methods)
+				->getMock();
+		}
+	}
+
+	public function dataCallTriggerCalendarActivity() {
+		return [
+			['onCalendarAdd', [['data']], Extension::SUBJECT_ADD, [['data'], [], []]],
+			['onCalendarUpdate', [['data'], ['shares'], ['changed-properties']], Extension::SUBJECT_UPDATE, [['data'], ['shares'], ['changed-properties']]],
+			['onCalendarDelete', [['data'], ['shares']], Extension::SUBJECT_DELETE, [['data'], ['shares'], []]],
+		];
+	}
+
+	/**
+	 * @dataProvider dataCallTriggerCalendarActivity
+	 *
+	 * @param string $method
+	 * @param array $payload
+	 * @param string $expectedSubject
+	 * @param array $expectedPayload
+	 */
+	public function testCallTriggerCalendarActivity($method, array $payload, $expectedSubject, array $expectedPayload) {
+		$backend = $this->getBackend(['triggerCalendarActivity']);
+		$backend->expects($this->once())
+			->method('triggerCalendarActivity')
+			->willReturnCallback(function() use($expectedPayload, $expectedSubject) {
+				$arguments = func_get_args();
+				$this->assertSame($expectedSubject, array_shift($arguments));
+				$this->assertEquals($expectedPayload, $arguments);
+			});
+
+		call_user_func_array([$backend, $method], $payload);
+	}
+
+	public function dataTriggerCalendarActivity() {
+		return [
+			// Add calendar
+			[Extension::SUBJECT_ADD, [], [], [], '', '', null, []],
+			[Extension::SUBJECT_ADD, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], [], [], '', 'admin', null, ['admin']],
+			[Extension::SUBJECT_ADD, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], [], [], 'test2', 'test2', null, ['admin']],
+
+			// Update calendar
+			[Extension::SUBJECT_UPDATE, [], [], [], '', '', null, []],
+			// No visible change - owner only
+			[Extension::SUBJECT_UPDATE, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], ['shares'], [], '', 'admin', null, ['admin']],
+			// Visible change
+			[Extension::SUBJECT_UPDATE, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], ['shares'], ['{DAV:}displayname' => 'Name'], '', 'admin', ['user1'], ['user1', 'admin']],
+			[Extension::SUBJECT_UPDATE, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], ['shares'], ['{DAV:}displayname' => 'Name'], 'test2', 'test2', ['user1'], ['user1', 'admin']],
+
+			// Delete calendar
+			[Extension::SUBJECT_DELETE, [], [], [], '', '', null, []],
+			[Extension::SUBJECT_DELETE, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], ['shares'], [], '', 'admin', [], ['admin']],
+			[Extension::SUBJECT_DELETE, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], ['shares'], [], '', 'admin', ['user1'], ['user1', 'admin']],
+			[Extension::SUBJECT_DELETE, [
+				'principaluri' => 'principal/user/admin',
+				'id' => 42,
+				'{DAV:}displayname' => 'Name of calendar',
+			], ['shares'], [], 'test2', 'test2', ['user1'], ['user1', 'admin']],
+		];
+	}
+
+	/**
+	 * @dataProvider dataTriggerCalendarActivity
+	 * @param string $action
+	 * @param array $data
+	 * @param array $shares
+	 * @param array $changedProperties
+	 * @param string $currentUser
+	 * @param string $author
+	 * @param string[]|null $shareUsers
+	 * @param string[] $users
+	 */
+	public function testTriggerCalendarActivity($action, array $data, array $shares, array $changedProperties, $currentUser, $author, $shareUsers, array $users) {
+		$backend = $this->getBackend(['getUsersForShares']);
+
+		if ($shareUsers === null) {
+			$backend->expects($this->never())
+				->method('getUsersForShares');
+		} else {
+			$backend->expects($this->once())
+				->method('getUsersForShares')
+				->with($shares)
+				->willReturn($shareUsers);
+		}
+
+		if ($author !== '') {
+			if ($currentUser !== '') {
+				$this->userSession->expects($this->once())
+					->method('getUser')
+					->willReturn($this->getUserMock($currentUser));
+			} else {
+				$this->userSession->expects($this->once())
+					->method('getUser')
+					->willReturn(null);
+			}
+
+			$event = $this->createMock(IEvent::class);
+			$this->activityManager->expects($this->once())
+				->method('generateEvent')
+				->willReturn($event);
+
+			$event->expects($this->once())
+				->method('setApp')
+				->with('dav')
+				->willReturnSelf();
+			$event->expects($this->once())
+				->method('setObject')
+				->with(Extension::CALENDAR, $data['id'])
+				->willReturnSelf();
+			$event->expects($this->once())
+				->method('setType')
+				->with(Extension::CALENDAR)
+				->willReturnSelf();
+			$event->expects($this->once())
+				->method('setAuthor')
+				->with($author)
+				->willReturnSelf();
+
+			$event->expects($this->exactly(sizeof($users)))
+				->method('setAffectedUser')
+				->willReturnSelf();
+			$event->expects($this->exactly(sizeof($users)))
+				->method('setSubject')
+				->willReturnSelf();
+			$this->activityManager->expects($this->exactly(sizeof($users)))
+				->method('publish')
+				->with($event);
+		} else {
+			$this->activityManager->expects($this->never())
+				->method('generateEvent');
+		}
+
+		$this->invokePrivate($backend, 'triggerCalendarActivity', [$action, $data, $shares, $changedProperties]);
+	}
+
+	public function dataGetUsersForShares() {
+		return [
+			[
+				[],
+				[],
+				[],
+			],
+			[
+				[
+					['{http://owncloud.org/ns}principal' => 'principal/users/user1'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user2'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user2'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user2'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user3'],
+				],
+				[],
+				['user1', 'user2', 'user3'],
+			],
+			[
+				[
+					['{http://owncloud.org/ns}principal' => 'principal/users/user1'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user2'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user2'],
+					['{http://owncloud.org/ns}principal' => 'principal/groups/group2'],
+					['{http://owncloud.org/ns}principal' => 'principal/groups/group3'],
+				],
+				['group2' => null, 'group3' => null],
+				['user1', 'user2'],
+			],
+			[
+				[
+					['{http://owncloud.org/ns}principal' => 'principal/users/user1'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user2'],
+					['{http://owncloud.org/ns}principal' => 'principal/users/user2'],
+					['{http://owncloud.org/ns}principal' => 'principal/groups/group2'],
+					['{http://owncloud.org/ns}principal' => 'principal/groups/group3'],
+				],
+				['group2' => ['user1', 'user2', 'user3'], 'group3' => ['user2', 'user3', 'user4']],
+				['user1', 'user2', 'user3', 'user4'],
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider dataGetUsersForShares
+	 * @param array $shares
+	 * @param array $groups
+	 * @param array $expected
+	 */
+	public function testGetUsersForShares(array $shares, array $groups, array $expected) {
+		$backend = $this->getBackend();
+
+		$getGroups = [];
+		foreach ($groups as $gid => $members) {
+			if ($members === null) {
+				$getGroups[] = [$gid, null];
+				continue;
+			}
+
+			$group = $this->createMock(IGroup::class);
+			$group->expects($this->once())
+				->method('getUsers')
+				->willReturn($this->getUsers($members));
+
+			$getGroups[] = [$gid, $group];
+		}
+
+		$this->groupManager->expects($this->exactly(sizeof($getGroups)))
+			->method('get')
+			->willReturnMap($getGroups);
+
+		$users = $this->invokePrivate($backend, 'getUsersForShares', [$shares]);
+		sort($users);
+		$this->assertEquals($expected, $users);
+	}
+
+	/**
+	 * @param string[] $users
+	 * @return IUser[]|\PHPUnit_Framework_MockObject_MockObject[]
+	 */
+	protected function getUsers(array $users) {
+		$list = [];
+		foreach ($users as $user) {
+			$list[] = $this->getUserMock($user);
+		}
+		return $list;
+	}
+
+	/**
+	 * @param string $uid
+	 * @return IUser|\PHPUnit_Framework_MockObject_MockObject
+	 */
+	protected function getUserMock($uid) {
+		$user = $this->createMock(IUser::class);
+		$user->expects($this->once())
+			->method('getUID')
+			->willReturn($uid);
+		return $user;
+	}
+}
diff --git a/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php b/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php
index 8349d98cd94bc..b5e700e8bc4f8 100644
--- a/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php
@@ -51,6 +51,9 @@ public function testCalendarOperations() {
 			'{DAV:}displayname' => 'Unit test',
 			'{urn:ietf:params:xml:ns:caldav}calendar-description' => 'Calendar used for unit testing'
 		]);
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::updateCalendar');
 		$this->backend->updateCalendar($calendarId, $patch);
 		$patch->commit();
 		$this->assertEquals(1, $this->backend->getCalendarsForUserCount(self::UNIT_TEST_USER));
@@ -60,6 +63,9 @@ public function testCalendarOperations() {
 		$this->assertEquals('Calendar used for unit testing', $books[0]['{urn:ietf:params:xml:ns:caldav}calendar-description']);
 
 		// delete the address book
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendar');
 		$this->backend->deleteCalendar($books[0]['id']);
 		$books = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
 		$this->assertEquals(0, count($books));
@@ -106,6 +112,9 @@ public function testCalendarSharing($userCanRead, $userCanWrite, $groupCanRead,
 		$books = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
 		$this->assertEquals(1, count($books));
 		$calendar = new Calendar($this->backend, $books[0], $l10n);
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::updateShares');
 		$this->backend->updateShares($calendar, $add, []);
 		$books = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER1);
 		$this->assertEquals(1, count($books));
@@ -138,6 +147,9 @@ public function testCalendarSharing($userCanRead, $userCanWrite, $groupCanRead,
 END:VCALENDAR
 EOD;
 
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject');
 		$this->backend->createCalendarObject($calendarId, $uri, $calData);
 
 		/** @var IACL $child */
@@ -151,6 +163,9 @@ public function testCalendarSharing($userCanRead, $userCanWrite, $groupCanRead,
 		$this->assertAccess($groupCanWrite, self::UNIT_TEST_GROUP, '{DAV:}write', $acl);
 
 		// delete the address book
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendar');
 		$this->backend->deleteCalendar($books[0]['id']);
 		$books = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER);
 		$this->assertEquals(0, count($books));
@@ -179,6 +194,9 @@ public function testCalendarObjectsOperations() {
 END:VCALENDAR
 EOD;
 
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject');
 		$this->backend->createCalendarObject($calendarId, $uri, $calData);
 
 		// get all the cards
@@ -214,11 +232,17 @@ public function testCalendarObjectsOperations() {
 END:VEVENT
 END:VCALENDAR
 EOD;
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::updateCalendarObject');
 		$this->backend->updateCalendarObject($calendarId, $uri, $calData);
 		$calendarObject = $this->backend->getCalendarObject($calendarId, $uri);
 		$this->assertEquals($calData, $calendarObject['calendardata']);
 
 		// delete the card
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject');
 		$this->backend->deleteCalendarObject($calendarId, $uri);
 		$calendarObjects = $this->backend->getCalendarObjects($calendarId);
 		$this->assertEquals(0, count($calendarObjects));
@@ -246,10 +270,19 @@ public function testMultiCalendarObjects() {
 END:VCALENDAR
 EOD;
 		$uri0 = $this->getUniqueID('card');
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject');
 		$this->backend->createCalendarObject($calendarId, $uri0, $calData);
 		$uri1 = $this->getUniqueID('card');
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject');
 		$this->backend->createCalendarObject($calendarId, $uri1, $calData);
 		$uri2 = $this->getUniqueID('card');
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject');
 		$this->backend->createCalendarObject($calendarId, $uri2, $calData);
 
 		// get all the cards
@@ -270,8 +303,17 @@ public function testMultiCalendarObjects() {
 		}
 
 		// delete the card
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject');
 		$this->backend->deleteCalendarObject($calendarId, $uri0);
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject');
 		$this->backend->deleteCalendarObject($calendarId, $uri1);
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject');
 		$this->backend->deleteCalendarObject($calendarId, $uri2);
 		$calendarObjects = $this->backend->getCalendarObjects($calendarId);
 		$this->assertEquals(0, count($calendarObjects));
@@ -335,6 +377,10 @@ public function testSyncSupport() {
 	}
 
 	public function testPublications() {
+		$this->dispatcher->expects($this->at(0))
+			->method('dispatch')
+			->with('\OCA\DAV\CalDAV\CalDavBackend::createCalendar');
+
 		$this->backend->createCalendar(self::UNIT_TEST_USER, 'Example', []);
 
 		$calendarInfo = $this->backend->getCalendarsForUser(self::UNIT_TEST_USER)[0];
@@ -357,10 +403,8 @@ public function testPublications() {
 		$calendar->setPublishStatus(false);
 		$this->assertEquals(false, $calendar->getPublishStatus());
 
-		$publicCalendarURI = md5($this->config->getSystemValue('secret', '') . $calendar->getResourceId());
 		$this->setExpectedException('Sabre\DAV\Exception\NotFound');
-		$publicCalendar = $this->backend->getPublicCalendar($publicCalendarURI);
-
+		$this->backend->getPublicCalendar($publicCalendarURI);
 	}
 
 	public function testSubscriptions() {
diff --git a/apps/dav/tests/unit/CalDAV/PublicCalendarRootTest.php b/apps/dav/tests/unit/CalDAV/PublicCalendarRootTest.php
index 6dfec6d7e1f0f..59fa4747a93b8 100644
--- a/apps/dav/tests/unit/CalDAV/PublicCalendarRootTest.php
+++ b/apps/dav/tests/unit/CalDAV/PublicCalendarRootTest.php
@@ -9,6 +9,7 @@
 use OCA\DAV\CalDAV\PublicCalendarRoot;
 use OCP\IUserManager;
 use OCP\Security\ISecureRandom;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Test\TestCase;
 
 /**
@@ -27,12 +28,11 @@ class PublicCalendarRootTest extends TestCase {
 	private $publicCalendarRoot;
 	/** @var IL10N */
 	private $l10n;
-	/** @var IUserManager */
-	private $userManager;
-	/** @var Principal */
+	/** @var Principal|\PHPUnit_Framework_MockObject_MockObject */
 	private $principal;
-	/** var IConfig */
-	protected $config;
+	/** @var IUserManager|\PHPUnit_Framework_MockObject_MockObject */
+	protected $userManager;
+
 	/** @var ISecureRandom */
 	private $random;
 
@@ -40,19 +40,17 @@ public function setUp() {
 		parent::setUp();
 
 		$db = \OC::$server->getDatabaseConnection();
-		$this->principal = $this->getMockBuilder('OCA\DAV\Connector\Sabre\Principal')
-			->disableOriginalConstructor()
-			->getMock();
-		$this->config = \OC::$server->getConfig();
-		$this->userManager = $this->getMockBuilder('\OCP\IUserManager')->getMock();
+		$this->principal = $this->createMock('OCA\DAV\Connector\Sabre\Principal');
+		$this->userManager = $this->createMock(IUserManager::class);
 		$this->random = \OC::$server->getSecureRandom();
+		$dispatcher = $this->createMock(EventDispatcherInterface::class);
 
 		$this->backend = new CalDavBackend(
 			$db,
 			$this->principal,
 			$this->userManager,
-			$this->config,
-			$this->random
+			$this->random,
+			$dispatcher
 		);
 
 		$this->publicCalendarRoot = new PublicCalendarRoot($this->backend);