diff --git a/apps/dav/appinfo/v1/caldav.php b/apps/dav/appinfo/v1/caldav.php
index ba49f2961f..ecd6a17123 100644
--- a/apps/dav/appinfo/v1/caldav.php
+++ b/apps/dav/appinfo/v1/caldav.php
@@ -46,10 +46,12 @@ $principalBackend = new Principal(
 	'principals/'
 );
 $db = \OC::$server->getDatabaseConnection();
-$config = \OC::$server->getConfig();
 $userManager = \OC::$server->getUserManager();
 $random = \OC::$server->getSecureRandom();
-$calDavBackend = new CalDavBackend($db, $principalBackend, $userManager, $config, $random);
+$groupManager = \OC::$server->getGroupManager();
+$activityManager = \OC::$server->getActivityManager();
+$userSession = \OC::$server->getUserSession();
+$calDavBackend = new CalDavBackend($db, $principalBackend, $userManager, $groupManager, $random, $activityManager, $userSession);
 
 $debugging = \OC::$server->getConfig()->getSystemValue('debug', false);
 
diff --git a/apps/dav/lib/AppInfo/Application.php b/apps/dav/lib/AppInfo/Application.php
index d073131f00..32483e8fd8 100644
--- a/apps/dav/lib/AppInfo/Application.php
+++ b/apps/dav/lib/AppInfo/Application.php
@@ -24,7 +24,7 @@
  */
 namespace OCA\DAV\AppInfo;
 
-use OCA\DAV\CalDAV\Activity;
+use OCA\DAV\CalDAV\Activity\Extension;
 use OCA\DAV\CalDAV\BirthdayService;
 use OCA\DAV\Capabilities;
 use OCA\DAV\CardDAV\ContactsManager;
@@ -92,7 +92,7 @@ class Application extends App {
 
 		$aM = $this->getContainer()->getServer()->getActivityManager();
 		$aM->registerExtension(function() {
-			return $this->getContainer()->query(Activity::class);
+			return $this->getContainer()->query(Extension::class);
 		});
 	}
 
diff --git a/apps/dav/lib/CalDAV/Activity/Backend.php b/apps/dav/lib/CalDAV/Activity/Backend.php
new file mode 100644
index 0000000000..9d931e0f55
--- /dev/null
+++ b/apps/dav/lib/CalDAV/Activity/Backend.php
@@ -0,0 +1,396 @@
+<?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 OCA\DAV\CalDAV\CalDavBackend;
+use OCA\DAV\CalDAV\Calendar;
+use OCP\Activity\IEvent;
+use OCP\Activity\IManager as IActivityManager;
+use OCP\IGroup;
+use OCP\IGroupManager;
+use OCP\IUser;
+use OCP\IUserSession;
+
+/**
+ * Class Backend
+ *
+ * @package OCA\DAV\CalDAV\Activity
+ */
+class Backend {
+
+	/** @var CalDavBackend */
+	protected  $calDavBackend;
+
+	/** @var IActivityManager */
+	protected $activityManager;
+
+	/** @var IGroupManager */
+	protected $groupManager;
+
+	/** @var IUserSession */
+	protected $userSession;
+
+	/**
+	 * @param CalDavBackend $calDavBackend
+	 * @param IActivityManager $activityManager
+	 * @param IGroupManager $groupManager
+	 * @param IUserSession $userSession
+	 */
+	public function __construct(CalDavBackend $calDavBackend, IActivityManager $activityManager, IGroupManager $groupManager, IUserSession $userSession) {
+		$this->calDavBackend = $calDavBackend;
+		$this->activityManager = $activityManager;
+		$this->groupManager = $groupManager;
+		$this->userSession = $userSession;
+	}
+
+	/**
+	 * Creates activities when a calendar was creates
+	 *
+	 * @param int $calendarId
+	 * @param array $properties
+	 */
+	public function addCalendar($calendarId, array $properties) {
+		$this->triggerActivity(Extension::SUBJECT_ADD, $calendarId, $properties);
+	}
+
+	/**
+	 * Creates activities when a calendar was updated
+	 *
+	 * @param int $calendarId
+	 * @param array $properties
+	 */
+	public function updateCalendar($calendarId, array $properties) {
+		$this->triggerActivity(Extension::SUBJECT_UPDATE, $calendarId, $properties);
+	}
+
+	/**
+	 * Creates activities when a calendar was deleted
+	 *
+	 * @param int $calendarId
+	 */
+	public function deleteCalendar($calendarId) {
+		$this->triggerActivity(Extension::SUBJECT_DELETE, $calendarId);
+	}
+
+
+	/**
+	 * Creates activities for all related users when a calendar was touched
+	 *
+	 * @param string $action
+	 * @param int $calendarId
+	 * @param array $changedProperties
+	 */
+	protected function triggerActivity($action, $calendarId, array $changedProperties = []) {
+		$properties = $this->calDavBackend->getCalendarById($calendarId);
+		if (!isset($properties['principaluri'])) {
+			return;
+		}
+
+		$principal = explode('/', $properties['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, $calendarId)
+			->setType(Extension::CALENDAR)
+			->setAuthor($currentUser);
+
+		$changedVisibleInformation = array_intersect([
+			'{DAV:}displayname',
+			'{http://apple.com/ns/ical/}calendar-color'
+		], array_keys($changedProperties));
+
+		if ($action === Extension::SUBJECT_UPDATE && empty($changedVisibleInformation)) {
+			$users = [$owner];
+		} else {
+			$users = $this->getUsersForCalendar($calendarId);
+			$users[] = $owner;
+		}
+
+		foreach ($users as $user) {
+			$event->setAffectedUser($user)
+				->setSubject(
+					$user === $currentUser ? $action . '_self' : $action,
+					[
+						$currentUser,
+						$properties['{DAV:}displayname'],
+					]
+				);
+			$this->activityManager->publish($event);
+		}
+	}
+
+	/**
+	 * Creates activities for all related users when a calendar was (un-)shared
+	 *
+	 * @param Calendar $calendar
+	 * @param array $add
+	 * @param array $remove
+	 */
+	public function updateCalendarShares(Calendar $calendar, array $add, array $remove) {
+		$calendarId = $calendar->getResourceId();
+		$shares = $this->calDavBackend->getShares($calendarId);
+
+		$properties = $this->calDavBackend->getCalendarById($calendarId);
+		$principal = explode('/', $properties['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, $calendarId)
+			->setType(Extension::CALENDAR)
+			->setAuthor($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,
+					$properties,
+					Extension::SUBJECT_UNSHARE_USER,
+					Extension::SUBJECT_DELETE . '_self'
+				);
+
+				if ($owner !== $principal[2]) {
+					$parameters = [
+						$principal[2],
+						$properties['{DAV:}displayname'],
+					];
+
+					if ($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, $properties, Extension::SUBJECT_UNSHARE_USER);
+
+				$parameters = [
+					$principal[2],
+					$properties['{DAV:}displayname'],
+				];
+
+				if ($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, $properties, Extension::SUBJECT_SHARE_USER);
+
+				if ($owner !== $principal[2]) {
+					$parameters = [
+						$principal[2],
+						$properties['{DAV:}displayname'],
+					];
+
+					if ($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, $properties, Extension::SUBJECT_SHARE_USER);
+
+				$parameters = [
+					$principal[2],
+					$properties['{DAV:}displayname'],
+				];
+
+				if ($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);
+	}
+
+	/**
+	 * Get all users that have access to a given calendar
+	 *
+	 * @param int $calendarId
+	 * @return string[]
+	 */
+	protected function getUsersForCalendar($calendarId) {
+		$users = $groups = [];
+		$shares = $this->calDavBackend->getShares($calendarId);
+		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 $users;
+	}
+}
diff --git a/apps/dav/lib/CalDAV/Activity.php b/apps/dav/lib/CalDAV/Activity/Extension.php
similarity index 98%
rename from apps/dav/lib/CalDAV/Activity.php
rename to apps/dav/lib/CalDAV/Activity/Extension.php
index b551a5f930..9100bb7e18 100644
--- a/apps/dav/lib/CalDAV/Activity.php
+++ b/apps/dav/lib/CalDAV/Activity/Extension.php
@@ -19,22 +19,19 @@
  *
  */
 
-namespace OCA\DAV\CalDAV;
+namespace OCA\DAV\CalDAV\Activity;
 
 use OCP\Activity\IExtension;
 use OCP\IURLGenerator;
 use OCP\L10N\IFactory;
 
-class Activity implements IExtension {
+class Extension implements IExtension {
 	const APP = 'dav';
 	/**
 	 * Filter with all sharing related activities
 	 */
 	const CALENDAR = 'calendar';
 
-	/**
-	 * Activity types known to this extension
-	 */
 	const SUBJECT_ADD = 'calendar_add';
 	const SUBJECT_UPDATE = 'calendar_update';
 	const SUBJECT_DELETE = 'calendar_delete';
@@ -43,10 +40,6 @@ class Activity implements IExtension {
 	const SUBJECT_UNSHARE_USER = 'calendar_user_unshare';
 	const SUBJECT_UNSHARE_GROUP = 'calendar_group_unshare';
 
-	/**
-	 * Subject keys for translation of the subjections
-	 */
-
 	/** @var IFactory */
 	protected $languageFactory;
 
diff --git a/apps/dav/lib/CalDAV/CalDavBackend.php b/apps/dav/lib/CalDAV/CalDavBackend.php
index 2d2a5062a0..fa01d27bef 100644
--- a/apps/dav/lib/CalDAV/CalDavBackend.php
+++ b/apps/dav/lib/CalDAV/CalDavBackend.php
@@ -26,16 +26,16 @@
 namespace OCA\DAV\CalDAV;
 
 use OCA\DAV\DAV\Sharing\IShareable;
-use OCP\Activity\IEvent;
+use OCA\DAV\CalDAV\Activity\Backend as ActivityBackend;
+use OCP\Activity\IManager as IActivityManager;
 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\IGroup;
 use OCP\IGroupManager;
 use OCP\IUser;
 use OCP\IUserManager;
+use OCP\IUserSession;
 use OCP\Security\ISecureRandom;
 use Sabre\CalDAV\Backend\AbstractBackend;
 use Sabre\CalDAV\Backend\SchedulingSupport;
@@ -127,32 +127,37 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 
 	/** @var IUserManager */
 	private $userManager;
-	
-	/** @var IConfig */
-	private $config;
 
 	/** @var ISecureRandom */
 	private $random;
 
+	/** @var ActivityBackend */
+	private $activityBackend;
+
 	/**
 	 * CalDavBackend constructor.
 	 *
 	 * @param IDBConnection $db
 	 * @param Principal $principalBackend
 	 * @param IUserManager $userManager
-	 * @param IConfig $config
+	 * @param IGroupManager $groupManager
 	 * @param ISecureRandom $random
+	 * @param IActivityManager $activityManager
+	 * @param IUserSession $userSession
 	 */
 	public function __construct(IDBConnection $db,
 								Principal $principalBackend,
 								IUserManager $userManager,
-								IConfig $config,
-								ISecureRandom $random) {
+								IGroupManager $groupManager,
+								ISecureRandom $random,
+								IActivityManager $activityManager,
+								IUserSession $userSession) {
 		$this->db = $db;
 		$this->principalBackend = $principalBackend;
 		$this->userManager = $userManager;
+		$this->userManager = $groupManager;
 		$this->sharingBackend = new Backend($this->db, $principalBackend, 'calendar');
-		$this->config = $config;
+		$this->activityBackend = new ActivityBackend($this, $activityManager, $groupManager, $userSession);
 		$this->random = $random;
 	}
 
@@ -618,7 +623,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		$query->execute();
 		$calendarId = $query->getLastInsertId();
 
-		$this->triggerActivity(Activity::SUBJECT_ADD, $calendarId, $values);
+		$this->activityBackend->addCalendar($calendarId, $values);
 
 		return $calendarId;
 	}
@@ -668,7 +673,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 
 			$this->addChange($calendarId, "", 2);
 
-			$this->triggerActivity(Activity::SUBJECT_UPDATE, $calendarId, $mutations);
+			$this->activityBackend->updateCalendar($calendarId, $mutations);
 
 			return true;
 		});
@@ -681,7 +686,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	 * @return void
 	 */
 	function deleteCalendar($calendarId) {
-		$this->triggerActivity(Activity::SUBJECT_DELETE, $calendarId);
+		$this->activityBackend->deleteCalendar($calendarId);
 
 		$stmt = $this->db->prepare('DELETE FROM `*PREFIX*calendarobjects` WHERE `calendarid` = ?');
 		$stmt->execute([$calendarId]);
@@ -1660,8 +1665,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	 */
 	public function updateShares($shareable, $add, $remove) {
 		/** @var Calendar $shareable */
-		$this->triggerActivitySharing($shareable, $add, $remove);
-
+		$this->activityBackend->updateCalendarShares($shareable, $add, $remove);
 		$this->sharingBackend->updateShares($shareable, $add, $remove);
 	}
 
@@ -1736,276 +1740,4 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		}
 		return $principalUri;
 	}
-
-	protected function triggerActivity($action, $calendarId, array $changedProperties = []) {
-		$aM = \OC::$server->getActivityManager();
-		$userSession = \OC::$server->getUserSession();
-
-		$properties = $this->getCalendarById($calendarId);
-		if (!isset($properties['principaluri'])) {
-			return;
-		}
-
-		$principal = explode('/', $properties['principaluri']);
-		$owner = $principal[2];
-
-		$currentUser = $userSession->getUser();
-		if ($currentUser instanceof IUser) {
-			$currentUser = $currentUser->getUID();
-		} else {
-			$currentUser = $owner;
-		}
-
-		$event = $aM->generateEvent();
-		$event->setApp('dav')
-			->setObject(Activity::CALENDAR, $calendarId)
-			->setType(Activity::CALENDAR)
-			->setAuthor($currentUser);
-
-		$changedVisibleInformation = array_intersect([
-			'{DAV:}displayname',
-			'{http://apple.com/ns/ical/}calendar-color'
-		], array_keys($changedProperties));
-
-		if ($action === Activity::SUBJECT_UPDATE && empty($changedVisibleInformation)) {
-			$users = [$owner];
-		} else {
-			$users = $this->getUsersForCalendar($calendarId);
-			$users[] = $owner;
-		}
-
-		foreach ($users as $user) {
-			$event->setAffectedUser($user)
-				->setSubject(
-					$user === $currentUser ? $action . '_self' : $action,
-					[
-						$currentUser,
-						$properties['{DAV:}displayname'],
-					]
-				);
-			$aM->publish($event);
-		}
-	}
-
-	protected function triggerActivitySharing(Calendar $calendar, array $add, array $remove) {
-		$aM = \OC::$server->getActivityManager();
-		$userSession = \OC::$server->getUserSession();
-
-		$calendarId = $calendar->getResourceId();
-		$shares = $this->sharingBackend->getShares($calendarId);
-
-		$properties = $this->getCalendarById($calendarId);
-		$principal = explode('/', $properties['principaluri']);
-		$owner = $principal[2];
-
-		$currentUser = $userSession->getUser();
-		if ($currentUser instanceof IUser) {
-			$currentUser = $currentUser->getUID();
-		} else {
-			$currentUser = $owner;
-		}
-
-		$event = $aM->generateEvent();
-		$event->setApp('dav')
-			->setObject(Activity::CALENDAR, $calendarId)
-			->setType(Activity::CALENDAR)
-			->setAuthor($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->triggerActivityUnshareUser(
-					$principal[2],
-					$event,
-					$properties,
-					Activity::SUBJECT_UNSHARE_USER,
-					Activity::SUBJECT_DELETE . '_self'
-				);
-
-				if ($owner !== $principal[2]) {
-					$parameters = [
-						$principal[2],
-						$properties['{DAV:}displayname'],
-					];
-
-					if ($owner === $event->getAuthor()) {
-						$subject = Activity::SUBJECT_UNSHARE_USER . '_you';
-					} else if ($principal[2] === $event->getAuthor()) {
-						$subject = Activity::SUBJECT_UNSHARE_USER . '_self';
-					} else {
-						$event->setAffectedUser($event->getAuthor())
-							->setSubject(Activity::SUBJECT_UNSHARE_USER . '_you', $parameters);
-						$aM->publish($event);
-
-						$subject = Activity::SUBJECT_UNSHARE_USER . '_by';
-						$parameters[] = $event->getAuthor();
-					}
-
-					$event->setAffectedUser($owner)
-						->setSubject($subject, $parameters);
-					$aM->publish($event);
-				}
-			} else if ($principal[1] === 'groups') {
-				$this->triggerActivityUnshareGroup($principal[2], $event, $properties, Activity::SUBJECT_UNSHARE_USER);
-
-				$parameters = [
-					$principal[2],
-					$properties['{DAV:}displayname'],
-				];
-
-				if ($owner === $event->getAuthor()) {
-					$subject = Activity::SUBJECT_UNSHARE_GROUP . '_you';
-				} else {
-					$event->setAffectedUser($event->getAuthor())
-						->setSubject(Activity::SUBJECT_UNSHARE_GROUP . '_you', $parameters);
-					$aM->publish($event);
-
-					$subject = Activity::SUBJECT_UNSHARE_GROUP . '_by';
-					$parameters[] = $event->getAuthor();
-				}
-
-				$event->setAffectedUser($owner)
-					->setSubject($subject, $parameters);
-				$aM->publish($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') {
-				$this->triggerActivityUnshareUser($principal[2], $event, $properties, Activity::SUBJECT_SHARE_USER);
-
-				if ($owner !== $principal[2]) {
-					$parameters = [
-						$principal[2],
-						$properties['{DAV:}displayname'],
-					];
-
-					if ($owner === $event->getAuthor()) {
-						$subject = Activity::SUBJECT_SHARE_USER . '_you';
-					} else {
-						$event->setAffectedUser($event->getAuthor())
-							->setSubject(Activity::SUBJECT_SHARE_USER . '_you', $parameters);
-						$aM->publish($event);
-
-						$subject = Activity::SUBJECT_SHARE_USER . '_by';
-						$parameters[] = $event->getAuthor();
-					}
-
-					$event->setAffectedUser($owner)
-						->setSubject($subject, $parameters);
-					$aM->publish($event);
-				}
-			} else if ($principal[1] === 'groups') {
-				$this->triggerActivityUnshareGroup($principal[2], $event, $properties, Activity::SUBJECT_SHARE_USER);
-
-				$parameters = [
-					$principal[2],
-					$properties['{DAV:}displayname'],
-				];
-
-				if ($owner === $event->getAuthor()) {
-					$subject = Activity::SUBJECT_SHARE_GROUP . '_you';
-				} else {
-					$event->setAffectedUser($event->getAuthor())
-						->setSubject(Activity::SUBJECT_SHARE_GROUP . '_you', $parameters);
-					$aM->publish($event);
-
-					$subject = Activity::SUBJECT_SHARE_GROUP . '_by';
-					$parameters[] = $event->getAuthor();
-				}
-
-				$event->setAffectedUser($owner)
-					->setSubject($subject, $parameters);
-				$aM->publish($event);
-			}
-		}
-	}
-
-	protected function isAlreadyShared($principal, $shares) {
-		foreach ($shares as $share) {
-			if ($principal === $share['href']) {
-				return true;
-			}
-		}
-		return false;
-	}
-
-	protected function triggerActivityUnshareGroup($gid, IEvent $event, array $properties, $subject) {
-		$gM = \OC::$server->getGroupManager();
-
-		$group = $gM->get($gid);
-		if ($group instanceof IGroup) {
-			foreach ($group->getUsers() as $user) {
-				// Exclude current user
-				if ($user->getUID() !== $event->getAuthor()) {
-					$this->triggerActivityUnshareUser($user->getUID(), $event, $properties, $subject);
-				}
-			}
-		}
-	}
-
-	protected function triggerActivityUnshareUser($user, IEvent $event, array $properties, $subject, $subjectSelf = '') {
-		$aM = \OC::$server->getActivityManager();
-
-		$event->setAffectedUser($user)
-			->setSubject(
-				$user === $event->getAuthor() && $subjectSelf ? $subjectSelf : $subject,
-				[
-					$event->getAuthor(),
-					$properties['{DAV:}displayname'],
-				]
-			);
-		$aM->publish($event);
-	}
-
-	/**
-	 * Get all users that have access to a given calendar
-	 *
-	 * @param int $calendarId
-	 * @return string[]
-	 */
-	protected function getUsersForCalendar($calendarId) {
-		$gM = \OC::$server->getGroupManager();
-
-		$users = $groups = [];
-		$shares = $this->getShares($calendarId);
-		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 = $gM->get($gid);
-				if ($group instanceof IGroup) {
-					foreach ($group->getUsers() as $user) {
-						$users[] = $user->getUID();
-					}
-				}
-			}
-		}
-
-		return $users;
-	}
 }
diff --git a/apps/dav/lib/Command/CreateCalendar.php b/apps/dav/lib/Command/CreateCalendar.php
index da1f706a8b..6fea608244 100644
--- a/apps/dav/lib/Command/CreateCalendar.php
+++ b/apps/dav/lib/Command/CreateCalendar.php
@@ -75,11 +75,12 @@ class CreateCalendar extends Command {
 			$this->userManager,
 			$this->groupManager
 		);
-		$config = \OC::$server->getConfig();
 		$random = \OC::$server->getSecureRandom();
+		$activityManager = \OC::$server->getActivityManager();
+		$userSession = \OC::$server->getUserSession();
 
 		$name = $input->getArgument('name');
-		$caldav = new CalDavBackend($this->dbConnection, $principalBackend, $this->userManager, $config, $random);
+		$caldav = new CalDavBackend($this->dbConnection, $principalBackend, $this->userManager, $this->groupManager, $random, $activityManager, $userSession);
 		$caldav->createCalendar("principals/users/$user", $name, []);
 	}
 }
diff --git a/apps/dav/lib/RootCollection.php b/apps/dav/lib/RootCollection.php
index 4c76dc30c3..38b4ec795d 100644
--- a/apps/dav/lib/RootCollection.php
+++ b/apps/dav/lib/RootCollection.php
@@ -41,6 +41,9 @@ class RootCollection extends SimpleCollection {
 		$config = \OC::$server->getConfig();
 		$random = \OC::$server->getSecureRandom();
 		$userManager = \OC::$server->getUserManager();
+		$groupManager = \OC::$server->getGroupManager();
+		$activityManager = \OC::$server->getActivityManager();
+		$userSession = \OC::$server->getUserSession();
 		$db = \OC::$server->getDatabaseConnection();
 		$dispatcher = \OC::$server->getEventDispatcher();
 		$userPrincipalBackend = new Principal(
@@ -62,7 +65,7 @@ class RootCollection extends SimpleCollection {
 		$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, $groupManager, $random, $activityManager, $userSession);
 		$calendarRoot = new CalendarRoot($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 2559ecbbf8..a674c65c28 100644
--- a/apps/dav/tests/unit/CalDAV/AbstractCalDavBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/AbstractCalDavBackendTest.php
@@ -22,18 +22,15 @@
 
 namespace OCA\DAV\Tests\unit\CalDAV;
 
-use DateTime;
-use DateTimeZone;
+use OCA\DAV\CalDAV\Activity\Backend as ActivityBackend;
 use OCA\DAV\CalDAV\CalDavBackend;
-use OCA\DAV\CalDAV\Calendar;
 use OCA\DAV\Connector\Sabre\Principal;
-use OCP\IL10N;
-use OCP\IConfig;
+use OCP\Activity\IManager as IActivityManager;
+use OCP\IGroupManager;
+use OCP\IUserManager;
+use OCP\IUserSession;
 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 Test\TestCase;
 
 /**
@@ -50,12 +47,10 @@ 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 ActivityBackend|\PHPUnit_Framework_MockObject_MockObject */
+	protected $activityBackend;
 
 	/** @var ISecureRandom */
 	private $random;
@@ -67,9 +62,10 @@ abstract class AbstractCalDavBackendTest extends TestCase {
 	public function setUp() {
 		parent::setUp();
 
-		$this->userManager = $this->getMockBuilder('OCP\IUserManager')
-			->disableOriginalConstructor()
-			->getMock();
+		$this->userManager = $this->createMock(IUserManager::class);
+		$groupManager = $this->createMock(IGroupManager::class);
+		$activityManager = $this->createMock(IActivityManager::class);
+		$userSession = $this->createMock(IUserSession::class);
 		$this->principal = $this->getMockBuilder('OCA\DAV\Connector\Sabre\Principal')
 			->disableOriginalConstructor()
 			->setMethods(['getPrincipalByPath', 'getGroupMembership'])
@@ -83,15 +79,21 @@ abstract class AbstractCalDavBackendTest extends TestCase {
 			->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, $groupManager, $this->random, $activityManager, $userSession);
+
+		$this->activityBackend = $this->createMock(ActivityBackend::class);
+		$this->invokePrivate($this->backend, 'activityBackend', [$this->activityBackend]);
+
+		$this->cleanUpBackend();
 	}
 
 	public function tearDown() {
+		$this->cleanUpBackend();
 		parent::tearDown();
+	}
 
+	public function cleanUpBackend() {
 		if (is_null($this->backend)) {
 			return;
 		}
diff --git a/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php b/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php
index 8349d98cd9..4d60e983b1 100644
--- a/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/CalDavBackendTest.php
@@ -357,10 +357,8 @@ EOD;
 		$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 6dfec6d7e1..c3a3d783e1 100644
--- a/apps/dav/tests/unit/CalDAV/PublicCalendarRootTest.php
+++ b/apps/dav/tests/unit/CalDAV/PublicCalendarRootTest.php
@@ -2,12 +2,16 @@
 
 namespace OCA\DAV\Tests\unit\CalDAV;
 
+use OCA\DAV\CalDAV\Activity\Backend as ActivityBackend;
 use OCA\DAV\CalDAV\Calendar;
 use OCA\DAV\Connector\Sabre\Principal;
+use OCP\Activity\IManager as IActivityManager;
+use OCP\IGroupManager;
 use OCP\IL10N;
 use OCA\DAV\CalDAV\CalDavBackend;
 use OCA\DAV\CalDAV\PublicCalendarRoot;
 use OCP\IUserManager;
+use OCP\IUserSession;
 use OCP\Security\ISecureRandom;
 use Test\TestCase;
 
@@ -27,12 +31,19 @@ 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 IGroupManager|\PHPUnit_Framework_MockObject_MockObject */
+	protected $groupManager;
+	/** @var IActivityManager|\PHPUnit_Framework_MockObject_MockObject */
+	protected $activityManager;
+	/** @var IUserSession|\PHPUnit_Framework_MockObject_MockObject */
+	protected $userSession;
+	/** @var ActivityBackend|\PHPUnit_Framework_MockObject_MockObject */
+	protected $activityBackend;
+
 	/** @var ISecureRandom */
 	private $random;
 
@@ -40,21 +51,26 @@ class PublicCalendarRootTest extends TestCase {
 		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);
+		$groupManager = $this->createMock(IGroupManager::class);
+		$activityManager = $this->createMock(IActivityManager::class);
+		$userSession = $this->createMock(IUserSession::class);
 		$this->random = \OC::$server->getSecureRandom();
 
 		$this->backend = new CalDavBackend(
 			$db,
 			$this->principal,
 			$this->userManager,
-			$this->config,
-			$this->random
+			$groupManager,
+			$this->random,
+			$activityManager,
+			$userSession
 		);
 
+		$this->activityBackend = $this->createMock(ActivityBackend::class);
+		$this->invokePrivate($this->backend, 'activityBackend', [$this->activityBackend]);
+
 		$this->publicCalendarRoot = new PublicCalendarRoot($this->backend);
 
 		$this->l10n = $this->getMockBuilder('\OCP\IL10N')
@@ -79,6 +95,14 @@ class PublicCalendarRootTest extends TestCase {
 	}
 
 	public function testGetChild() {
+		$this->activityBackend->expects($this->exactly(1))
+			->method('addCalendar');
+		$this->activityBackend->expects($this->never())
+			->method('updateCalendar');
+		$this->activityBackend->expects($this->never())
+			->method('deleteCalendar');
+		$this->activityBackend->expects($this->never())
+			->method('updateCalendarShares');
 
 		$calendar = $this->createPublicCalendar();
 
@@ -93,6 +117,15 @@ class PublicCalendarRootTest extends TestCase {
 	}
 
 	public function testGetChildren() {
+		$this->activityBackend->expects($this->exactly(1))
+			->method('addCalendar');
+		$this->activityBackend->expects($this->never())
+			->method('updateCalendar');
+		$this->activityBackend->expects($this->never())
+			->method('deleteCalendar');
+		$this->activityBackend->expects($this->never())
+			->method('updateCalendarShares');
+
 		$this->createPublicCalendar();
 
 		$publicCalendars = $this->backend->getPublicCalendars();