diff --git a/apps/dav/lib/CalDAV/Activity/Provider/Base.php b/apps/dav/lib/CalDAV/Activity/Provider/Base.php
new file mode 100644
index 0000000000..43c3403c5b
--- /dev/null
+++ b/apps/dav/lib/CalDAV/Activity/Provider/Base.php
@@ -0,0 +1,129 @@
+<?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\Provider;
+
+use OCP\Activity\IEvent;
+use OCP\Activity\IProvider;
+use OCP\IUser;
+use OCP\IUserManager;
+
+abstract class Base implements IProvider {
+
+	/** @var IUserManager */
+	protected $userManager;
+
+	/** @var string[] cached displayNames - key is the UID and value the displayname */
+	protected $displayNames = [];
+
+	/**
+	 * @param IUserManager $userManager
+	 */
+	public function __construct(IUserManager $userManager) {
+		$this->userManager = $userManager;
+	}
+
+	/**
+	 * @param IEvent $event
+	 * @param string $subject
+	 * @param array $parameters
+	 */
+	protected function setSubjects(IEvent $event, $subject, array $parameters) {
+		$placeholders = $replacements = [];
+		foreach ($parameters as $placeholder => $parameter) {
+			$placeholders[] = '{' . $placeholder . '}';
+			$replacements[] = $parameter['name'];
+		}
+
+		$event->setParsedSubject(str_replace($placeholders, $replacements, $subject))
+			->setRichSubject($subject, $parameters);
+	}
+
+	/**
+	 * @param array $eventData
+	 * @return array
+	 */
+	protected function generateObjectParameter($eventData) {
+		if (!is_array($eventData)) {
+			throw new \InvalidArgumentException();
+		};
+
+		return [
+			'type' => 'calendar-event',
+			'id' => $eventData['id'],
+			'name' => $eventData['name'],
+		];
+	}
+
+	/**
+	 * @param int $id
+	 * @param string $name
+	 * @return array
+	 */
+	protected function generateCalendarParameter($id, $name) {
+		return [
+			'type' => 'calendar',
+			'id' => $id,
+			'name' => $name,
+		];
+	}
+
+	/**
+	 * @param string $id
+	 * @return array
+	 */
+	protected function generateGroupParameter($id) {
+		return [
+			'type' => 'group',
+			'id' => $id,
+			'name' => $id,
+		];
+	}
+
+	/**
+	 * @param string $uid
+	 * @return array
+	 */
+	protected function generateUserParameter($uid) {
+		if (!isset($this->displayNames[$uid])) {
+			$this->displayNames[$uid] = $this->getDisplayName($uid);
+		}
+
+		return [
+			'type' => 'user',
+			'id' => $uid,
+			'name' => $this->displayNames[$uid],
+		];
+	}
+
+	/**
+	 * @param string $uid
+	 * @return string
+	 */
+	protected function getDisplayName($uid) {
+		$user = $this->userManager->get($uid);
+		if ($user instanceof IUser) {
+			return $user->getDisplayName();
+		} else {
+			return $uid;
+		}
+	}
+}
diff --git a/apps/dav/lib/CalDAV/Activity/Provider/Calendar.php b/apps/dav/lib/CalDAV/Activity/Provider/Calendar.php
index 05881866ce..2e2ce5bc27 100644
--- a/apps/dav/lib/CalDAV/Activity/Provider/Calendar.php
+++ b/apps/dav/lib/CalDAV/Activity/Provider/Calendar.php
@@ -24,13 +24,11 @@ namespace OCA\DAV\CalDAV\Activity\Provider;
 use OCP\Activity\IEvent;
 use OCP\Activity\IEventMerger;
 use OCP\Activity\IManager;
-use OCP\Activity\IProvider;
 use OCP\IL10N;
 use OCP\IURLGenerator;
-use OCP\IUser;
 use OCP\IUserManager;
 
-class Calendar implements IProvider {
+class Calendar extends Base {
 
 	const SUBJECT_ADD = 'calendar_add';
 	const SUBJECT_UPDATE = 'calendar_update';
@@ -49,15 +47,9 @@ class Calendar implements IProvider {
 	/** @var IManager */
 	protected $activityManager;
 
-	/** @var IUserManager */
-	protected $userManager;
-
 	/** @var IEventMerger */
 	protected $eventMerger;
 
-	/** @var string[] cached displayNames - key is the UID and value the displayname */
-	protected $displayNames = [];
-
 	/**
 	 * @param IL10N $l
 	 * @param IURLGenerator $url
@@ -66,10 +58,10 @@ class Calendar implements IProvider {
 	 * @param IEventMerger $eventMerger
 	 */
 	public function __construct(IL10N $l, IURLGenerator $url, IManager $activityManager, IUserManager $userManager, IEventMerger $eventMerger) {
+		parent::__construct($userManager);
 		$this->l = $l;
 		$this->url = $url;
 		$this->activityManager = $activityManager;
-		$this->userManager = $userManager;
 		$this->eventMerger = $eventMerger;
 	}
 
@@ -145,22 +137,6 @@ class Calendar implements IProvider {
 		return $event;
 	}
 
-	/**
-	 * @param IEvent $event
-	 * @param string $subject
-	 * @param array $parameters
-	 */
-	protected function setSubjects(IEvent $event, $subject, array $parameters) {
-		$placeholders = $replacements = [];
-		foreach ($parameters as $placeholder => $parameter) {
-			$placeholders[] = '{' . $placeholder . '}';
-			$replacements[] = $parameter['name'];
-		}
-
-		$event->setParsedSubject(str_replace($placeholders, $replacements, $subject))
-			->setRichSubject($subject, $parameters);
-	}
-
 	/**
 	 * @param IEvent $event
 	 * @return array
@@ -213,58 +189,4 @@ class Calendar implements IProvider {
 
 		throw new \InvalidArgumentException();
 	}
-
-	/**
-	 * @param string $id
-	 * @return array
-	 */
-	protected function generateGroupParameter($id) {
-		return [
-			'type' => 'group',
-			'id' => $id,
-			'name' => $id,
-		];
-	}
-
-	/**
-	 * @param int $id
-	 * @param string $name
-	 * @return array
-	 */
-	protected function generateCalendarParameter($id, $name) {
-		return [
-			'type' => 'calendar',
-			'id' => $id,
-			'name' => $name,
-		];
-	}
-
-	/**
-	 * @param string $uid
-	 * @return array
-	 */
-	protected function generateUserParameter($uid) {
-		if (!isset($this->displayNames[$uid])) {
-			$this->displayNames[$uid] = $this->getDisplayName($uid);
-		}
-
-		return [
-			'type' => 'user',
-			'id' => $uid,
-			'name' => $this->displayNames[$uid],
-		];
-	}
-
-	/**
-	 * @param string $uid
-	 * @return string
-	 */
-	protected function getDisplayName($uid) {
-		$user = $this->userManager->get($uid);
-		if ($user instanceof IUser) {
-			return $user->getDisplayName();
-		} else {
-			return $uid;
-		}
-	}
 }
diff --git a/apps/dav/lib/CalDAV/Activity/Provider/Event.php b/apps/dav/lib/CalDAV/Activity/Provider/Event.php
index 1bad07916b..11c8d901ac 100644
--- a/apps/dav/lib/CalDAV/Activity/Provider/Event.php
+++ b/apps/dav/lib/CalDAV/Activity/Provider/Event.php
@@ -24,13 +24,11 @@ namespace OCA\DAV\CalDAV\Activity\Provider;
 use OCP\Activity\IEvent;
 use OCP\Activity\IEventMerger;
 use OCP\Activity\IManager;
-use OCP\Activity\IProvider;
 use OCP\IL10N;
 use OCP\IURLGenerator;
-use OCP\IUser;
 use OCP\IUserManager;
 
-class Event implements IProvider {
+class Event extends Base {
 
 	const SUBJECT_OBJECT_ADD = 'object_add';
 	const SUBJECT_OBJECT_UPDATE = 'object_update';
@@ -45,15 +43,9 @@ class Event implements IProvider {
 	/** @var IManager */
 	protected $activityManager;
 
-	/** @var IUserManager */
-	protected $userManager;
-
 	/** @var IEventMerger */
 	protected $eventMerger;
 
-	/** @var string[] cached displayNames - key is the UID and value the displayname */
-	protected $displayNames = [];
-
 	/**
 	 * @param IL10N $l
 	 * @param IURLGenerator $url
@@ -62,10 +54,10 @@ class Event implements IProvider {
 	 * @param IEventMerger $eventMerger
 	 */
 	public function __construct(IL10N $l, IURLGenerator $url, IManager $activityManager, IUserManager $userManager, IEventMerger $eventMerger) {
+		parent::__construct($userManager);
 		$this->l = $l;
 		$this->url = $url;
 		$this->activityManager = $activityManager;
-		$this->userManager = $userManager;
 		$this->eventMerger = $eventMerger;
 	}
 
@@ -107,22 +99,6 @@ class Event implements IProvider {
 		return $event;
 	}
 
-	/**
-	 * @param IEvent $event
-	 * @param string $subject
-	 * @param array $parameters
-	 */
-	protected function setSubjects(IEvent $event, $subject, array $parameters) {
-		$placeholders = $replacements = [];
-		foreach ($parameters as $placeholder => $parameter) {
-			$placeholders[] = '{' . $placeholder . '}';
-			$replacements[] = $parameter['name'];
-		}
-
-		$event->setParsedSubject(str_replace($placeholders, $replacements, $subject))
-			->setRichSubject($subject, $parameters);
-	}
-
 	/**
 	 * @param IEvent $event
 	 * @return array
@@ -151,62 +127,4 @@ class Event implements IProvider {
 
 		throw new \InvalidArgumentException();
 	}
-
-	/**
-	 * @param array $eventData
-	 * @return array
-	 */
-	protected function generateObjectParameter($eventData) {
-		if (!is_array($eventData)) {
-			throw new \InvalidArgumentException();
-		};
-
-		return [
-			'type' => 'calendar-event',
-			'id' => $eventData['id'],
-			'name' => $eventData['name'],
-		];
-	}
-
-	/**
-	 * @param int $id
-	 * @param string $name
-	 * @return array
-	 */
-	protected function generateCalendarParameter($id, $name) {
-		return [
-			'type' => 'calendar',
-			'id' => $id,
-			'name' => $name,
-		];
-	}
-
-	/**
-	 * @param string $uid
-	 * @return array
-	 */
-	protected function generateUserParameter($uid) {
-		if (!isset($this->displayNames[$uid])) {
-			$this->displayNames[$uid] = $this->getDisplayName($uid);
-		}
-
-		return [
-			'type' => 'user',
-			'id' => $uid,
-			'name' => $this->displayNames[$uid],
-		];
-	}
-
-	/**
-	 * @param string $uid
-	 * @return string
-	 */
-	protected function getDisplayName($uid) {
-		$user = $this->userManager->get($uid);
-		if ($user instanceof IUser) {
-			return $user->getDisplayName();
-		} else {
-			return $uid;
-		}
-	}
 }
diff --git a/apps/dav/lib/CalDAV/Activity/Provider/Todo.php b/apps/dav/lib/CalDAV/Activity/Provider/Todo.php
index 12c341160c..43ab9e9c44 100644
--- a/apps/dav/lib/CalDAV/Activity/Provider/Todo.php
+++ b/apps/dav/lib/CalDAV/Activity/Provider/Todo.php
@@ -22,13 +22,6 @@
 namespace OCA\DAV\CalDAV\Activity\Provider;
 
 use OCP\Activity\IEvent;
-use OCP\Activity\IEventMerger;
-use OCP\Activity\IManager;
-use OCP\Activity\IProvider;
-use OCP\IL10N;
-use OCP\IURLGenerator;
-use OCP\IUser;
-use OCP\IUserManager;
 
 class Todo extends Event {