diff --git a/application/config/routes.php b/application/config/routes.php
index aa4ba9db8..6a8d2b8fb 100644
--- a/application/config/routes.php
+++ b/application/config/routes.php
@@ -119,6 +119,10 @@ $route['api/frontend/v1/stv/[sS]tudents/([WS]S[0-9]{4})/prestudent/(:num)'] = 'a
 // // (studiensemester_kurzbz)/person/(person_id)
 $route['api/frontend/v1/stv/[sS]tudents/([WS]S[0-9]{4})/person/(:num)'] = 'api/frontend/v1/stv/Students/getPerson/$1/$2';
 
+
+$route['test'] = 'Test';
+$route['test/.*'] = 'Test';
+
 // load routes from extensions, also look for environment-specific configs
 $subdirs = ['application/config/extensions', 'application/config/' . ENVIRONMENT . '/extensions'];
 
diff --git a/application/controllers/Test.php b/application/controllers/Test.php
new file mode 100644
index 000000000..0454d16f4
--- /dev/null
+++ b/application/controllers/Test.php
@@ -0,0 +1,145 @@
+<?php
+
+if (! defined('BASEPATH')) exit('No direct script access allowed');
+
+/**
+ */
+class Test extends FHC_Controller
+{
+	/**
+	 * Constructor
+	 */
+	public function __construct()
+	{
+        parent::__construct();
+		$this->load->library('sabredav/SabreDAVAuthLib');
+        $this->load->library('sabredav/SabreDAVCalDAVLib');
+	}
+
+	// -----------------------------------------------------------------------------------------------------------------
+	// Public methods
+	public function index()
+	{
+       
+        $authBackend = new SabreDAVAuthLib();
+        $principalBackend = new SabreDAVACLPrincipalBackendLib($authBackend);
+        $calendarBackend = new SabreDAVCalDAVBackendLib($authBackend);
+
+        $tree = array(
+            new \Sabre\CalDAV\Principal\Collection($principalBackend),
+            new SabreDAVReadOnlyCalendarRootLib($principalBackend, $calendarBackend)
+        );
+
+        $server = new \Sabre\DAV\Server($tree);
+
+        $path = "/ma1433/core/FHC-Core/index.ci.php/test"; 
+        $server->setBaseUri($path);
+
+        $authBackend->setRealm('SabreDAV');
+        $authPlugin = new \Sabre\DAV\Auth\Plugin($authBackend);
+        $server->addPlugin($authPlugin);
+
+        $this->_registerReadOnlyWriteInterceptor($server);
+
+        $caldavPlugin = new \Sabre\CalDAV\Plugin();
+        $server->addPlugin($caldavPlugin);
+
+        $aclPlugin = new \Sabre\DAVACL\Plugin();
+        $server->addPlugin($aclPlugin);
+
+        $browser = new \Sabre\DAV\Browser\Plugin();
+        $server->addPlugin($browser);
+
+        $server->exec();
+	}
+
+	private function _registerReadOnlyWriteInterceptor($server)
+	{
+		$callback = function() use ($server) {
+			return $this->_discardReadOnlyWriteRequest($server, func_get_args());
+		};
+
+		if (method_exists($server, 'on'))
+		{
+			$server->on('beforeMethod', $callback, 20);
+			return;
+		}
+
+		if (method_exists($server, 'subscribeEvent'))
+		{
+			$server->subscribeEvent('beforeMethod', $callback, 20);
+		}
+	}
+
+	private function _discardReadOnlyWriteRequest($server, array $eventArgs)
+	{
+		$method = $this->_getDavRequestMethod($eventArgs);
+		if (!in_array($method, array('PUT', 'DELETE', 'PROPPATCH', 'MKCOL', 'MOVE', 'COPY'), true))
+			return true;
+
+		$this->_sendReadOnlyWriteAcceptedResponse($server, $eventArgs);
+		return false;
+	}
+
+	private function _getDavRequestMethod(array $eventArgs)
+	{
+		foreach ($eventArgs as $argument)
+		{
+			if (is_string($argument))
+				return strtoupper($argument);
+
+			if (is_object($argument) && method_exists($argument, 'getMethod'))
+				return strtoupper($argument->getMethod());
+		}
+
+		return isset($_SERVER['REQUEST_METHOD']) ? strtoupper($_SERVER['REQUEST_METHOD']) : '';
+	}
+
+	private function _sendReadOnlyWriteAcceptedResponse($server, array $eventArgs)
+	{
+		$response = $this->_getDavResponse($server, $eventArgs);
+
+		if (is_object($response))
+		{
+			if (method_exists($response, 'setStatus'))
+			{
+				$response->setStatus(204);
+				if (method_exists($response, 'setHeader'))
+					$response->setHeader('Content-Length', '0');
+				if (method_exists($response, 'setBody'))
+					$response->setBody('');
+				return;
+			}
+
+			if (method_exists($response, 'sendStatus'))
+			{
+				if (method_exists($response, 'setHeader'))
+					$response->setHeader('Content-Length', '0');
+				$response->sendStatus(204);
+				return;
+			}
+		}
+
+		if (!headers_sent())
+		{
+			header('HTTP/1.1 204 No Content');
+			header('Content-Length: 0');
+		}
+	}
+
+	private function _getDavResponse($server, array $eventArgs)
+	{
+		foreach ($eventArgs as $argument)
+		{
+			if (is_object($argument) && (
+				method_exists($argument, 'setStatus')
+				|| method_exists($argument, 'sendStatus')
+			))
+			{
+				return $argument;
+			}
+		}
+
+		return isset($server->httpResponse) ? $server->httpResponse : null;
+	}
+}
diff --git a/application/controllers/api/frontend/v1/tempus/Kalender.php b/application/controllers/api/frontend/v1/tempus/Kalender.php
index d1aeaa576..d6050c65c 100644
--- a/application/controllers/api/frontend/v1/tempus/Kalender.php
+++ b/application/controllers/api/frontend/v1/tempus/Kalender.php
@@ -38,8 +38,8 @@ class Kalender extends FHCAPI_Controller
 
 		$this->_ci->load->library('LogLib');
 		$this->_ci->load->library('form_validation');
-		$this->_ci->load->library('KalenderLib');
-		$this->_ci->load->library('RaumvorschlagLib');
+		$this->_ci->load->library('KalenderLib', ["uid" => getAuthUID()]);
+		$this->_ci->load->library('RaumvorschlagLib', ["uid" => getAuthUID()]);
 		$this->loadPhrases([
 			'ui'
 		]);
diff --git a/application/controllers/api/frontend/v1/tempus/OperationalResourceToCalenderAPI.php b/application/controllers/api/frontend/v1/tempus/OperationalResourceToCalenderAPI.php
index 376a0fedc..4f6a356f1 100644
--- a/application/controllers/api/frontend/v1/tempus/OperationalResourceToCalenderAPI.php
+++ b/application/controllers/api/frontend/v1/tempus/OperationalResourceToCalenderAPI.php
@@ -18,8 +18,8 @@ class OperationalResourceToCalenderAPI extends FHCAPI_Controller
 		$this->load->model('ressource/Betriebsmittel_model', 'BetriebsmittelModel');
 		$this->load->model('ressource/Kalender_model', 'KalenderModel');
 
-		$this->load->library('CollisionChecker');
-		$this->load->library('KalenderLib');
+		$this->_ci->load->library('CollisionChecker', ["uid" => getAuthUID()]);
+		$this->_ci->load->library('KalenderLib', ["uid" => getAuthUID()]);
 	}
 
 	//------------------------------------------------------------------------------------------------------------------
diff --git a/application/controllers/api/frontend/v1/tempus/Reservierung.php b/application/controllers/api/frontend/v1/tempus/Reservierung.php
index c1030d8ee..0215bcc8e 100644
--- a/application/controllers/api/frontend/v1/tempus/Reservierung.php
+++ b/application/controllers/api/frontend/v1/tempus/Reservierung.php
@@ -22,7 +22,7 @@ class Reservierung extends FHCAPI_Controller
 
 		$this->_ci->load->library('LogLib');
 		$this->_ci->load->library('form_validation');
-		$this->_ci->load->library('KalenderLib');
+		$this->_ci->load->library('KalenderLib', ["uid" => getAuthUID()]);
 
 		$this->_ci->load->model('ressource/Ort_model', 'OrtModel');
 		$this->_ci->load->model('ressource/Kalender_Event_Rolle_model', 'KalenderEventRolleModel');
diff --git a/application/libraries/CollisionChecker.php b/application/libraries/CollisionChecker.php
index ac9152d2b..6f4e7e6f4 100644
--- a/application/libraries/CollisionChecker.php
+++ b/application/libraries/CollisionChecker.php
@@ -9,16 +9,23 @@ class CollisionChecker
 	private $_checks = [];
 
 	private $_ci;
+	private $_uid;
 
-	public function __construct()
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
 
-		$this->_ci->load->library('collision/checks/RoomCollisionCheck');
-		$this->_ci->load->library('collision/checks/LectureCollisionCheck');
-		$this->_ci->load->library('collision/checks/VerbandCollisionCheck');
-		$this->_ci->load->library('collision/checks/StudentCollisionCheck');
-		$this->_ci->load->library('collision/checks/ResourcesCollisionCheck');
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
+
+		$this->_ci->load->library('collision/checks/RoomCollisionCheck', ['uid' => $this->_uid]);
+		$this->_ci->load->library('collision/checks/LectureCollisionCheck', ['uid' => $this->_uid]);
+		$this->_ci->load->library('collision/checks/VerbandCollisionCheck', ['uid' => $this->_uid]);
+		$this->_ci->load->library('collision/checks/StudentCollisionCheck', ['uid' => $this->_uid]);
+		$this->_ci->load->library('collision/checks/ResourcesCollisionCheck', ['uid' => $this->_uid]);
 		$this->register($this->_ci->roomcollisioncheck);
 		$this->register($this->_ci->lecturecollisioncheck);
 		$this->register($this->_ci->verbandcollisioncheck);
@@ -64,4 +71,4 @@ class CollisionChecker
 
 		return $results;
 	}
-}
\ No newline at end of file
+}
diff --git a/application/libraries/KalenderLib.php b/application/libraries/KalenderLib.php
index b0b3ad0ad..87c6d94e0 100644
--- a/application/libraries/KalenderLib.php
+++ b/application/libraries/KalenderLib.php
@@ -5,9 +5,17 @@ if (! defined("BASEPATH")) exit("No direct script access allowed");
 class KalenderLib
 {
 	private $_ci;
-	public function __construct()
+	private $_uid;
+
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
+		
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
 
 		$this->_ci->load->model('ressource/Kalender_model', 'KalenderModel');
 		$this->_ci->load->model('ressource/Kalender_Lehreinheit_model', 'KalenderLehreinheitModel');
@@ -22,7 +30,7 @@ class KalenderLib
 		$this->_ci->load->model('organisation/gruppe_model', 'GruppeModel');
 		$this->_ci->load->model('organisation/Lehrverband_model', 'LehrverbandModel');
 
-		$this->_ci->load->library('CollisionChecker');
+		$this->_ci->load->library('CollisionChecker', ['uid' => $this->_uid]);
 		$this->_ci->load->library('PhrasesLib', array('ui'));
 
 	}
@@ -180,7 +188,8 @@ class KalenderLib
 					'beschreibung' => isset($row->beschreibung) ? $row->beschreibung : '',
 					'topic' => (isset($row->lehrfach_kurzbz) ? $row->lehrfach_kurzbz : '').' '.(isset($row->lehrform_kurzbz) ? $row->lehrform_kurzbz : ''),
 					'collisions' => false,
-					'has_assigned_resources' => isset($row->has_assigned_resources) ? $row->has_assigned_resources : false
+					'has_assigned_resources' => isset($row->has_assigned_resources) ? $row->has_assigned_resources : false,
+					'updateamum' => isset($row->updateamum) ? $row->updateamum : null,
 				];
 			}
 
@@ -376,6 +385,134 @@ class KalenderLib
 		return $this->_mapEvents($data);
 	}
 
+	public function getPlanForStudentByStudent($start_date, $end_date, $userUID)
+	{
+		$this->_getBasePlan($start_date, $end_date);
+
+		$escapedUserUID = $this->_ci->KalenderModel->db->escape($userUID);
+
+		$benutzerExists = "EXISTS (
+			SELECT 1
+			FROM public.tbl_benutzer student_benutzer
+			WHERE student_benutzer.uid = $escapedUserUID
+		)";
+
+		$directEventTeilnehmerExists = "EXISTS (
+			SELECT 1
+			FROM lehre.tbl_kalender_event_teilnehmer event_teilnehmer
+			WHERE event_teilnehmer.kalender_id = tbl_kalender.kalender_id
+				AND event_teilnehmer.rolle_kurzbz = 'teilnehmer'
+				AND event_teilnehmer.uid = $escapedUserUID
+		)";
+
+		$eventBenutzergruppeExists = "EXISTS (
+			SELECT 1
+			FROM lehre.tbl_kalender_event_teilnehmer event_gruppe
+			JOIN public.tbl_benutzergruppe event_benutzergruppe
+				ON event_benutzergruppe.gruppe_kurzbz = event_gruppe.gruppe_kurzbz
+				AND (
+					event_gruppe.studiensemester_kurzbz IS NULL
+					OR event_benutzergruppe.studiensemester_kurzbz = event_gruppe.studiensemester_kurzbz
+				)
+			WHERE event_gruppe.kalender_id = tbl_kalender.kalender_id
+				AND event_gruppe.rolle_kurzbz = 'teilnehmer'
+				AND event_gruppe.gruppe_kurzbz IS NOT NULL
+				AND event_benutzergruppe.uid = $escapedUserUID
+		)";
+
+		$eventStudentlehrverbandExists = "EXISTS (
+			SELECT 1
+			FROM lehre.tbl_kalender_event_teilnehmer event_lehrverband
+			JOIN public.tbl_studentlehrverband event_studentlehrverband
+				ON event_studentlehrverband.student_uid = $escapedUserUID
+				AND event_studentlehrverband.studiengang_kz = event_lehrverband.studiengang_kz
+				AND (
+					event_lehrverband.studiensemester_kurzbz IS NULL
+					OR event_studentlehrverband.studiensemester_kurzbz = event_lehrverband.studiensemester_kurzbz
+				)
+				AND (
+					event_lehrverband.semester IS NULL
+					OR event_studentlehrverband.semester = event_lehrverband.semester
+				)
+				AND (
+					event_lehrverband.verband = event_studentlehrverband.verband
+					OR event_lehrverband.verband IS NULL
+					OR btrim(event_lehrverband.verband::text) = ''
+					OR event_studentlehrverband.verband IS NULL
+				)
+				AND (
+					event_lehrverband.gruppe = event_studentlehrverband.gruppe
+					OR event_lehrverband.gruppe IS NULL
+					OR btrim(event_lehrverband.gruppe::text) = ''
+					OR event_studentlehrverband.gruppe IS NULL
+				)
+			WHERE event_lehrverband.kalender_id = tbl_kalender.kalender_id
+				AND event_lehrverband.rolle_kurzbz = 'teilnehmer'
+				AND event_lehrverband.gruppe_kurzbz IS NULL
+				AND event_lehrverband.studiengang_kz IS NOT NULL
+		)";
+
+		$lehreinheitBenutzergruppeExists = "EXISTS (
+			SELECT 1
+			FROM lehre.tbl_kalender_lehreinheit student_kalender_lehreinheit
+			JOIN lehre.tbl_lehreinheit student_lehreinheit
+				ON student_lehreinheit.lehreinheit_id = student_kalender_lehreinheit.lehreinheit_id
+			JOIN lehre.tbl_lehreinheitgruppe student_lehreinheitgruppe
+				ON student_lehreinheitgruppe.lehreinheit_id = student_lehreinheit.lehreinheit_id
+			JOIN public.tbl_gruppe student_gruppe
+				ON student_gruppe.studiengang_kz = student_lehreinheitgruppe.studiengang_kz
+				AND student_gruppe.semester = student_lehreinheitgruppe.semester
+				AND student_gruppe.gruppe_kurzbz = student_lehreinheitgruppe.gruppe_kurzbz
+			JOIN public.tbl_benutzergruppe student_benutzergruppe
+				ON student_benutzergruppe.gruppe_kurzbz = student_gruppe.gruppe_kurzbz
+				AND student_benutzergruppe.studiensemester_kurzbz = student_lehreinheit.studiensemester_kurzbz
+			WHERE student_kalender_lehreinheit.kalender_id = tbl_kalender.kalender_id
+				AND student_lehreinheitgruppe.gruppe_kurzbz IS NOT NULL
+				AND student_benutzergruppe.uid = $escapedUserUID
+		)";
+
+		$lehreinheitStudentlehrverbandExists = "EXISTS (
+			SELECT 1
+			FROM lehre.tbl_kalender_lehreinheit student_kalender_lehreinheit
+			JOIN lehre.tbl_lehreinheit student_lehreinheit
+				ON student_lehreinheit.lehreinheit_id = student_kalender_lehreinheit.lehreinheit_id
+			JOIN lehre.tbl_lehreinheitgruppe student_lehreinheitgruppe
+				ON student_lehreinheitgruppe.lehreinheit_id = student_lehreinheit.lehreinheit_id
+			JOIN public.tbl_studentlehrverband student_lehrverband
+				ON student_lehrverband.student_uid = $escapedUserUID
+				AND student_lehrverband.studiengang_kz = student_lehreinheitgruppe.studiengang_kz
+				AND student_lehrverband.semester = student_lehreinheitgruppe.semester
+				AND student_lehrverband.studiensemester_kurzbz = student_lehreinheit.studiensemester_kurzbz
+				AND (
+					student_lehreinheitgruppe.verband = student_lehrverband.verband
+					OR student_lehreinheitgruppe.verband IS NULL
+					OR btrim(student_lehreinheitgruppe.verband::text) = ''
+					OR student_lehrverband.verband IS NULL
+				)
+				AND (
+					student_lehreinheitgruppe.gruppe = student_lehrverband.gruppe
+					OR student_lehreinheitgruppe.gruppe IS NULL
+					OR btrim(student_lehreinheitgruppe.gruppe::text) = ''
+					OR student_lehrverband.gruppe IS NULL
+				)
+			WHERE student_kalender_lehreinheit.kalender_id = tbl_kalender.kalender_id
+				AND student_lehreinheitgruppe.gruppe_kurzbz IS NULL
+		)";
+
+		$this->_ci->KalenderModel->db->where('status_kurzbz', 'live');
+		$this->_ci->KalenderModel->db->where($benutzerExists, null, false);
+		$this->_ci->KalenderModel->db->group_start();
+		$this->_ci->KalenderModel->db->where($directEventTeilnehmerExists, null, false);
+		$this->_ci->KalenderModel->db->or_where($eventBenutzergruppeExists, null, false);
+		$this->_ci->KalenderModel->db->or_where($eventStudentlehrverbandExists, null, false);
+		$this->_ci->KalenderModel->db->or_where($lehreinheitBenutzergruppeExists, null, false);
+		$this->_ci->KalenderModel->db->or_where($lehreinheitStudentlehrverbandExists, null, false);
+		$this->_ci->KalenderModel->db->group_end();
+
+		$data = $this->_ci->KalenderModel->load();
+
+		return $this->_mapEvents($data);
+	}
 
 	public function getPlanForLecturer($start_date, $end_date)
 	{
@@ -395,6 +532,42 @@ class KalenderLib
 
 		return $this->_mapEvents($data);
 	}
+
+	public function getPlanForLecturerByLecturer($start_date, $end_date, $userUID)
+	{
+		$this->_getBasePlan($start_date, $end_date);
+
+		$escapedUserUID = $this->_ci->KalenderModel->db->escape($userUID);
+
+		$lehreinheitMitarbeiterExists = "EXISTS (
+			SELECT 1
+			FROM lehre.tbl_kalender_lehreinheit lecturer_kalender_lehreinheit
+			JOIN lehre.tbl_lehreinheit lecturer_lehreinheit
+				ON lecturer_lehreinheit.lehreinheit_id = lecturer_kalender_lehreinheit.lehreinheit_id
+			JOIN lehre.tbl_lehreinheitmitarbeiter lecturer_lehreinheitmitarbeiter
+				ON lecturer_lehreinheitmitarbeiter.lehreinheit_id = lecturer_lehreinheit.lehreinheit_id
+			WHERE lecturer_kalender_lehreinheit.kalender_id = tbl_kalender.kalender_id
+				AND lecturer_lehreinheitmitarbeiter.mitarbeiter_uid = $escapedUserUID
+		)";
+
+		$eventTeilnehmerExists = "EXISTS (
+			SELECT 1
+			FROM lehre.tbl_kalender_event_teilnehmer lecturer_event_teilnehmer
+			WHERE lecturer_event_teilnehmer.kalender_id = tbl_kalender.kalender_id
+				AND lecturer_event_teilnehmer.uid = $escapedUserUID
+		)";
+
+		$this->_ci->KalenderModel->db->where('tbl_kalender.status_kurzbz', 'live');
+		$this->_ci->KalenderModel->db->group_start();
+		$this->_ci->KalenderModel->db->where($lehreinheitMitarbeiterExists, null, false);
+		$this->_ci->KalenderModel->db->or_where($eventTeilnehmerExists, null, false);
+		$this->_ci->KalenderModel->db->group_end();
+		
+		$data = $this->_ci->KalenderModel->load();
+
+		return $this->_mapEvents($data);
+	}
+
 	public function getZeitsperren($start_date, $end_date, $emp)
 	{
 		$db = new DB_Model();
@@ -593,6 +766,7 @@ class KalenderLib
 				'bis' => $end_date,
 				'typ' => 'reservierung',
 				'status_kurzbz' => 'live',
+				'eindeutige_gruppen_id' => $this->_ci->KalenderModel->generateUniqueGroupId(),
 				'insertvon' => getAuthUID(),
 				'insertamum' => date('Y-m-d H:i:s')
 			)
diff --git a/application/libraries/RaumvorschlagLib.php b/application/libraries/RaumvorschlagLib.php
index 3ff37e34b..fbdf7db3a 100644
--- a/application/libraries/RaumvorschlagLib.php
+++ b/application/libraries/RaumvorschlagLib.php
@@ -7,10 +7,18 @@ use CI3_Events as Events;
 class RaumvorschlagLib
 {
 	private $_ci;
-	public function __construct()
+	private $_uid;
+
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
 
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
+
 		$this->_ci->load->model('ressource/Kalender_model', 'KalenderModel');
 		$this->_ci->load->model('ressource/Kalender_Lehreinheit_model', 'KalenderLehreinheitModel');
 		$this->_ci->load->model('ressource/Kalender_Event_model', 'KalenderEventModel');
@@ -26,8 +34,8 @@ class RaumvorschlagLib
 		$this->_ci->load->model('education/Lehreinheitgruppe_model', 'LehreinheitgruppeModel');
 		$this->_ci->load->model('education/Lehreinheitgruppe_model', 'LehreinheitgruppeModel');
 
-		$this->_ci->load->library('CollisionChecker');
-		$this->_ci->load->library('KalenderLib');
+		$this->_ci->load->library('CollisionChecker', ["uid" => getAuthUID()]);
+		$this->_ci->load->library('KalenderLib', ["uid" => getAuthUID()]);
 		$this->_ci->load->library('PhrasesLib', array('ui'));
 	}
 
diff --git a/application/libraries/VariableLib.php b/application/libraries/VariableLib.php
index a503eb999..f5176ea67 100644
--- a/application/libraries/VariableLib.php
+++ b/application/libraries/VariableLib.php
@@ -14,9 +14,9 @@ class VariableLib
 	/**
 	 * VariableLib constructor.
 	 * Loads variable of logged in user.
-	 * @param $loggeduid
+	 * @param $params
 	 */
-	public function __construct($loggeduid)
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
 
@@ -25,8 +25,8 @@ class VariableLib
 		$this->_ci->load->model('system/Variable_model', 'VariableModel');
 		$this->_ci->load->model('organisation/studiensemester_model', 'StudiensemesterModel');
 
-		if (isset($loggeduid['uid']) && !isEmptyString($loggeduid['uid']))
-			$this->_setVariables($loggeduid['uid']);
+		if (isset($params['uid']) && !isEmptyString($params['uid']))
+			$this->_setVariables($params['uid']);
 		else
 		{
 			show_error('uid of logged user not passed!');
diff --git a/application/libraries/collision/checks/LectureCollisionCheck.php b/application/libraries/collision/checks/LectureCollisionCheck.php
index ff8303adb..34d26a09b 100644
--- a/application/libraries/collision/checks/LectureCollisionCheck.php
+++ b/application/libraries/collision/checks/LectureCollisionCheck.php
@@ -4,13 +4,21 @@ class LectureCollisionCheck implements ICollisionCheck
 {
 
 	private $_ci;
+	private $_uid;
 
-	public function __construct()
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
+		
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
+
 		$this->_ci->load->model('ressource/Kalender_model', 'KalenderModel');
 		$this->_ci->load->model('ressource/zeitsperre_model', 'ZeitsperreModel');
-		$this->_ci->load->library('VariableLib', array('uid' => getAuthUID()));
+		$this->_ci->load->library('VariableLib', ['uid' => $this->_uid]);
 		$this->_ci->load->library('PhrasesLib', array('ui'));
 
 	}
@@ -255,4 +263,4 @@ class LectureCollisionCheck implements ICollisionCheck
 		}, getData($result));
 	}
 
-}
\ No newline at end of file
+}
diff --git a/application/libraries/collision/checks/ResourcesCollisionCheck.php b/application/libraries/collision/checks/ResourcesCollisionCheck.php
index 0be789b7f..765ea286c 100644
--- a/application/libraries/collision/checks/ResourcesCollisionCheck.php
+++ b/application/libraries/collision/checks/ResourcesCollisionCheck.php
@@ -4,12 +4,20 @@ class ResourcesCollisionCheck implements ICollisionCheck
 {
 
 	private $_ci;
+	private $_uid;
 
-	public function __construct()
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
+		
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
+
 		$this->_ci->load->model('ressource/Kalender_model', 'KalenderModel');
-		$this->_ci->load->library('VariableLib', array('uid' => getAuthUID()));
+		$this->_ci->load->library('VariableLib', array('uid' => $this->_uid));
 		$this->_ci->load->library('PhrasesLib', array('ui'));
 	}
 
@@ -82,4 +90,4 @@ class ResourcesCollisionCheck implements ICollisionCheck
 
 		return $grouped;
 	}
-}
\ No newline at end of file
+}
diff --git a/application/libraries/collision/checks/RoomCollisionCheck.php b/application/libraries/collision/checks/RoomCollisionCheck.php
index 4d72ce0cd..f16891107 100644
--- a/application/libraries/collision/checks/RoomCollisionCheck.php
+++ b/application/libraries/collision/checks/RoomCollisionCheck.php
@@ -4,12 +4,20 @@ class RoomCollisionCheck implements ICollisionCheck
 {
 
 	private $_ci;
+	private $_uid;
 
-	public function __construct()
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
+		
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
+
 		$this->_ci->load->model('ressource/Kalender_model', 'KalenderModel');
-		$this->_ci->load->library('VariableLib', array('uid' => getAuthUID()));
+		$this->_ci->load->library('VariableLib', array('uid' => $this->_uid));
 		$this->_ci->load->library('PhrasesLib', array('ui'));
 	}
 
@@ -77,4 +85,4 @@ class RoomCollisionCheck implements ICollisionCheck
 
 		return $grouped;
 	}
-}
\ No newline at end of file
+}
diff --git a/application/libraries/collision/checks/StudentCollisionCheck.php b/application/libraries/collision/checks/StudentCollisionCheck.php
index 4ffeb071e..96a62b237 100644
--- a/application/libraries/collision/checks/StudentCollisionCheck.php
+++ b/application/libraries/collision/checks/StudentCollisionCheck.php
@@ -3,12 +3,20 @@
 class StudentCollisionCheck implements ICollisionCheck
 {
 	private $_ci;
+	private $_uid;
 
-	public function __construct()
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
+		
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
+
 		$this->_ci->load->model('ressource/Kalender_model', 'KalenderModel');
-		$this->_ci->load->library('VariableLib', array('uid' => getAuthUID()));
+		$this->_ci->load->library('VariableLib', array('uid' => $this->_uid));
 		$this->_ci->load->library('PhrasesLib', array('ui'));
 	}
 
@@ -244,4 +252,4 @@ class StudentCollisionCheck implements ICollisionCheck
 
 		return $grouped;
 	}
-}
\ No newline at end of file
+}
diff --git a/application/libraries/collision/checks/VerbandCollisionCheck.php b/application/libraries/collision/checks/VerbandCollisionCheck.php
index 40baf38a2..9284312b5 100644
--- a/application/libraries/collision/checks/VerbandCollisionCheck.php
+++ b/application/libraries/collision/checks/VerbandCollisionCheck.php
@@ -4,12 +4,20 @@ class VerbandCollisionCheck implements ICollisionCheck
 {
 
 	private $_ci;
+	private $_uid;
 
-	public function __construct()
+	public function __construct($params)
 	{
 		$this->_ci =& get_instance();
+		
+		if (isset($params['uid']) && !isEmptyString($params['uid'])){
+			$this->_uid = $params['uid'];
+		} else {
+			show_error('uid of logged user not passed!');
+		}
+
 		$this->_ci->load->model('ressource/Kalender_model', 'KalenderModel');
-		$this->_ci->load->library('VariableLib', array('uid' => getAuthUID()));
+		$this->_ci->load->library('VariableLib', array('uid' => $this->_uid));
 		$this->_ci->load->library('PhrasesLib', array('ui'));
 
 	}
@@ -359,4 +367,4 @@ class VerbandCollisionCheck implements ICollisionCheck
 		return $grouped;
 	}
 
-}
\ No newline at end of file
+}
diff --git a/application/libraries/sabredav/SabreDAVAuthLib.php b/application/libraries/sabredav/SabreDAVAuthLib.php
new file mode 100644
index 000000000..65b99e0c7
--- /dev/null
+++ b/application/libraries/sabredav/SabreDAVAuthLib.php
@@ -0,0 +1,38 @@
+<?php
+
+class SabreDAVAuthLib extends \Sabre\DAV\Auth\Backend\AbstractBasic
+{
+	private $_ci;
+	protected $currentUser = null;
+
+	public function __construct()
+	{
+		$this->_ci =& get_instance();
+		
+		$this->_ci->load->library('AuthLib', array(false));
+		$this->_ci->load->helper('hlp_authentication');
+	}
+
+	public function getCurrentUser()
+	{
+		if ($this->currentUser)
+			return $this->currentUser;
+
+		if (isLogged())
+			return getAuthUID();
+
+		return null;
+	}
+
+	protected function validateUserPass($username, $password)
+	{
+		if (isSuccess($this->_ci->authlib->checkUserAuthByUsernamePassword($username, $password)))
+		{
+			$this->currentUser = $username;
+			return true;
+		}
+
+		$this->currentUser = null;
+		return false;
+	}
+}
\ No newline at end of file
diff --git a/application/libraries/sabredav/SabreDAVCalDAVLib.php b/application/libraries/sabredav/SabreDAVCalDAVLib.php
new file mode 100644
index 000000000..e79f8a6e6
--- /dev/null
+++ b/application/libraries/sabredav/SabreDAVCalDAVLib.php
@@ -0,0 +1,971 @@
+<?php
+
+/**
+ * SabreDAV CalDAV classes for the LVPlan calendar endpoint.
+ */
+class SabreDAVCalDAVLib
+{
+}
+
+/**
+ * PDO principal backend
+ *
+ * This is a simple principal backend that maps exactly to the users table, as
+ * used by Sabre_DAV_Auth_Backend_PDO.
+ *
+ * It assumes all principals are in a single collection. The default collection
+ * is 'principals/', but this can be overriden.
+ *
+ * @package Sabre
+ * @subpackage DAVACL
+ * @copyright Copyright (C) 2007-2011 Rooftop Solutions. All rights reserved.
+ * @author Evert Pot (http://www.rooftopsolutions.nl/)
+ * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
+ */
+class SabreDAVACLPrincipalBackendLib implements \Sabre\DAVACL\PrincipalBackend\BackendInterface
+{
+    /**
+     * PDO table name for 'principals'
+     *
+     * @var string
+     */
+    protected $tableName;
+
+    /**
+     * PDO table name for 'group members'
+     *
+     * @var string
+     */
+    protected $groupMembersTableName;
+
+	protected $result_ma;
+	protected $auth;
+    /**
+     * Sets up the backend.
+     *
+     * @param PDO $pdo
+     * @param string $tableName
+     */
+    public function __construct($auth)
+	{
+		$this->auth = $auth;
+
+		/*
+		$ma = new mitarbeiter();
+		$this->result_ma = $ma->getMitarbeiter(null,null,null);
+		*/
+    }
+
+	/**
+	 * Liefert den eingeloggten User
+	 */
+	function getUser()
+	{
+		return $this->auth->getCurrentUser();
+	}
+
+
+    /**
+     * Returns a list of principals based on a prefix.
+     *
+     * This prefix will often contain something like 'principals'. You are only
+     * expected to return principals that are in this base path.
+     *
+     * You are expected to return at least a 'uri' for every user, you can
+     * return any additional properties if you wish so. Common properties are:
+     *   {DAV:}displayname
+     *   {http://sabredav.org/ns}email-address - This is a custom SabreDAV
+     *     field that's actualy injected in a number of other properties. If
+     *     you have an email address, use this property.
+     *
+     * @param string $prefixPath
+     * @return array
+     */
+    public function getPrincipalsByPrefix($prefixPath)
+	{
+		//$prefixPath = principals
+		//error_log('Principal.php/getPrincipalsByPrefix('.$prefixPath.')');
+        $principals = array();
+		$user = $this->getUser();
+
+		if($prefixPath=='principals')
+		{
+
+		    $principals[] = array(
+					'id' => $user,
+		            'uri' => 'principals/'.$user,
+		            '{DAV:}displayname' => $user,
+		            '{http://sabredav.org/ns}email-address' => $user.'@example.com',
+		        );
+		}
+
+        return $principals;
+
+    }
+
+    /**
+     * Returns a specific principal, specified by it's path.
+     * The returned structure should be the exact same as from
+     * getPrincipalsByPrefix.
+     *
+     * @param string $path
+     * @return array
+     */
+    public function getPrincipalByPath($path)
+	{
+		$user = mb_substr($path,11);
+
+        $result = array(
+            'id'  => $user,
+            'uri' => 'principals/'.$user,
+            '{DAV:}displayname' => $user,
+            '{http://sabredav.org/ns}email-address' => $user.'@example.com',
+        );
+
+		return $result;
+    }
+
+    /**
+     * Returns the list of members for a group-principal
+     *
+     * @param string $principal
+     * @return array
+     */
+    public function getGroupMemberSet($principal)
+	{
+        $result = array();
+
+		return $result;
+    }
+
+    /**
+     * Returns the list of groups a principal is a member of
+     *
+     * @param string $principal
+     * @return array
+     */
+    public function getGroupMembership($principal)
+	{
+		$result = array();
+		if(preg_match('/^principals\/[0-9A-Za-z\-]*$/',$principal))
+		{
+			$user = mb_substr($principal,11);
+		}
+        return $result;
+
+    }
+
+    /**
+     * Updates the list of group members for a group principal.
+     *
+     * The principals should be passed as a list of uri's.
+     *
+     * @param string $principal
+     * @param array $members
+     * @return void
+     */
+    public function setGroupMemberSet($principal, array $members)
+	{
+		throw new \Sabre\DAV\Exception('Not implemented');
+    }
+
+   public function updatePrincipal($path, \Sabre\DAV\PropPatch $propPatch)
+   {
+	$propPatch->setRemainingResultCode(403);
+   }
+
+	public function searchPrincipals($prefixPath, array $searchProperties, $test = 'allof')
+	{
+		return array();
+	}
+
+	public function findByUri($uri, $principalPrefix)
+	{
+		return null;
+	}
+}
+
+/**
+ * CalDAV backend
+ */
+class SabreDAVCalDAVBackendLib extends \Sabre\CalDAV\Backend\AbstractBackend
+{
+	protected $auth;
+
+	protected $CI;
+
+	/**
+     * Creates the backend
+     *
+     * @param AuthBackend $auth
+     */
+    public function __construct($auth)
+	{
+		$this->auth = $auth;
+
+		$this->CI =& get_instance();
+    }
+
+	/**
+	 * Liefert den eingeloggten User
+	 */
+	function getUser()
+	{
+		return $this->auth->getCurrentUser();
+	}
+
+    /**
+     * Returns a list of calendars for a principal.
+     *
+     * Every project is an array with the following keys:
+     *  * id, a unique id that will be used by other functions to modify the
+     *    calendar. This can be the same as the uri or a database key.
+     *  * uri, which the basename of the uri with which the calendar is
+     *    accessed.
+     *  * principalUri. The owner of the calendar. Almost always the same as
+     *    principalUri passed to this method.
+     *
+     * Furthermore it can contain webdav properties in clark notation. A very
+     * common one is '{DAV:}displayname'.
+     *
+     * @param string $principalUri
+     * @return array
+     */
+    public function getCalendarsForUser($principalUri)
+	{
+		$user = mb_substr($principalUri,11);
+        $calendars = array();
+		$calendar = array(
+			'id' => $user,
+			'uri' => 'LVPlan-'.$user,
+			'principaluri' => 'principals/'.$user,
+			'{' . \Sabre\CalDAV\Plugin::NS_CALENDARSERVER . '}getctag' => $this->buildCalendarCtag($user),
+			'{' . \Sabre\CalDAV\Plugin::NS_CALDAV . '}supported-calendar-component-set' => new \Sabre\CalDAV\Xml\Property\SupportedCalendarComponentSet(array('VEVENT')),
+			'{DAV:}displayname'                          => 'LVPlan',
+			'{urn:ietf:params:xml:ns:caldav}calendar-description' => 'description comes here',
+			'{urn:ietf:params:xml:ns:caldav}calendar-timezone'    => 'Europe/Vienna',
+			'{http://apple.com/ns/ical/}calendar-order'  => '1',
+			'{http://apple.com/ns/ical/}calendar-color'  => '#FF0000',
+			'{http://sabredav.org/ns}read-only' => 1
+        );
+		$calendars[] = $calendar;
+
+        return $calendars;
+    }
+
+    /**
+     * Creates a new calendar for a principal.
+     *
+     * If the creation was a success, an id must be returned that can be used to reference
+     * this calendar in other methods, such as updateCalendar
+     *
+     * @param string $principalUri
+     * @param string $calendarUri
+     * @param array $properties
+     */
+    public function createCalendar($principalUri,$calendarUri, array $properties)
+	{
+		return $calendarUri;
+    }
+
+    /**
+     * Updates properties for a calendar.
+     *
+     * The mutations array uses the propertyName in clark-notation as key,
+     * and the array value for the property value. In the case a property
+     * should be deleted, the property value will be null.
+     *
+     * This method must be atomic. If one property cannot be changed, the
+     * entire operation must fail.
+     *
+     * If the operation was successful, true can be returned.
+     * If the operation failed, false can be returned.
+     *
+     * Deletion of a non-existant property is always succesful.
+     *
+     * Lastly, it is optional to return detailed information about any
+     * failures. In this case an array should be returned with the following
+     * structure:
+     *
+     * array(
+     *   403 => array(
+     *      '{DAV:}displayname' => null,
+     *   ),
+     *   424 => array(
+     *      '{DAV:}owner' => null,
+     *   )
+     * )
+     *
+     * In this example it was forbidden to update {DAV:}displayname.
+     * (403 Forbidden), which in turn also caused {DAV:}owner to fail
+     * (424 Failed Dependency) because the request needs to be atomic.
+     *
+     * @param string $calendarId
+     * @param array $mutations
+     * @return bool|array
+     */
+    public function updateCalendar($calendarId, \Sabre\DAV\PropPatch $propPatch)
+	{
+        $propPatch->setRemainingResultCode(200);
+    }
+
+    /**
+     * Delete a calendar and all it's objects
+     *
+     * @param string $calendarId
+     * @return void
+     */
+    public function deleteCalendar($calendarId)
+	{
+		return null;
+    }
+
+
+	public function getCalendarData($userUID, $objectUri=null)
+	{
+		$this->CI->load->model("ressource/Mitarbeiter_model", "MitarbeiterModel");
+		$this->CI->load->model("person/Benutzer_model", "BenutzerModel");
+
+		$user = $this->CI->BenutzerModel->loadWhere(array("uid" => $userUID));
+		if(!$user)
+			die('User invalid');
+
+		$this->CI->load->library('KalenderLib', ['uid' => $userUID]);
+
+		$isUserEmployeeResult = $this->CI->MitarbeiterModel->isMitarbeiter($userUID);
+		if (isError($isUserEmployeeResult)) {
+			return;
+		}
+		$isUserEmployee = getData($isUserEmployeeResult);
+
+		$startDate = date('Y-m-d', mktime(0,0,0,date('m'),date('d')-14,date('Y')));
+		$endDate = date('Y-m-d', mktime(0,0,0,date('m')+6,date('d'),date('Y')));
+
+		$data = [];
+
+		if ($isUserEmployee) {
+			$data = $this->CI->kalenderlib->getPlanForLecturerByLecturer($startDate, $endDate, $userUID);
+		} else {
+			$data = $this->CI->kalenderlib->getPlanForStudentByStudent($startDate, $endDate, $userUID);
+		}
+
+		if(!is_array($data))
+			$data = array();
+
+		foreach($data as $item)
+		{
+			$item->calendarDataFragment = $this->buildCalendarDataFragment($item);
+		}
+
+		if (is_null($objectUri))
+		{
+			return $data;
+		}
+
+		$normalizedObjectUri = $this->normalizeObjectUri($objectUri);
+		foreach($data as $row)
+		{
+			if(md5($row->eindeutige_gruppen_id) == $normalizedObjectUri)
+			{
+				return $row;
+			}
+		}
+
+		return null;
+	}
+
+	public function makeCal($event)
+	{
+		return $this->buildICalLine('BEGIN', 'VCALENDAR')
+			.$this->buildICalLine('VERSION', '2.0')
+			.$this->buildICalTextLine('PRODID', 'FH Technikum Wien')
+			.$this->buildICalLine('BEGIN', 'VTIMEZONE')
+			.$this->buildICalLine('TZID', 'Europe/Vienna')
+			.$this->buildICalLine('BEGIN', 'DAYLIGHT')
+			.$this->buildICalLine('TZOFFSETFROM', '+0100')
+			.$this->buildICalLine('RRULE', 'FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU')
+			.$this->buildICalLine('DTSTART', '19810329T020000')
+			.$this->buildICalLine('TZNAME', 'GMT+02:00')
+			.$this->buildICalLine('TZOFFSETTO', '+0200')
+			.$this->buildICalLine('END', 'DAYLIGHT')
+			.$this->buildICalLine('BEGIN', 'STANDARD')
+			.$this->buildICalLine('TZOFFSETFROM', '+0200')
+			.$this->buildICalLine('RRULE', 'FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU')
+			.$this->buildICalLine('DTSTART', '19961027T030000')
+			.$this->buildICalLine('TZNAME', 'GMT+01:00')
+			.$this->buildICalLine('TZOFFSETTO', '+0100')
+			.$this->buildICalLine('END', 'STANDARD')
+			.$this->buildICalLine('END', 'VTIMEZONE')
+			.$event
+			.$this->buildICalLine('END', 'VCALENDAR');
+	}
+
+	protected function buildCalendarDataFragment($item)
+	{
+		$summary = $item->type == 'reservierung' ? $item->titel : $item->topic;
+
+		$description = "";
+		if ($item->type == 'reservierung') {
+			$description = $item->beschreibung;
+		} else {
+			$description = $item->lehrfach_bez . "\r\n";
+
+			if (isset($item->lektor) && is_array($item->lektor) && count($item->lektor) > 0) {
+				$description .= "Lehrer: " . join(", ", array_map(function($teacher) { return $teacher["kurzbz"]; }, $item->lektor)) . "\r\n";
+			}
+		}
+
+		$parsedStartDate = $this->formatICalLocalDateTime($item->isostart);
+		$parsedEndDate = $this->formatICalLocalDateTime($item->isoend);
+		$lastModified = $this->formatICalUtcDateTime(isset($item->updateamum) ? $item->updateamum : null);
+		$dtStamp = $lastModified ?: $this->formatICalUtcDateTime($item->isostart);
+
+		if($dtStamp === null)
+			$dtStamp = '19700101T000000Z';
+
+		$fragment = $this->buildICalLine('BEGIN', 'VEVENT')
+			.$this->buildICalTextLine('UID', $item->eindeutige_gruppen_id)
+			.$this->buildICalLine('SEQUENCE', (int)$item->kalender_id)
+			.$this->buildICalTextLine('SUMMARY', $summary)
+			.$this->buildICalTextLine('DESCRIPTION', 'TODO')
+			.$this->buildICalTextLine('LOCATION', isset($item->ort_kurzbz) ? $item->ort_kurzbz : '')
+			.$this->buildICalTextLine('CATEGORIES', 'Stundenplans')
+			.$this->buildICalLine('DTSTART', $parsedStartDate, array('TZID' => 'Europe/Vienna'))
+			.$this->buildICalLine('DTEND', $parsedEndDate, array('TZID' => 'Europe/Vienna'));
+
+		if($lastModified !== null)
+			$fragment .= $this->buildICalLine('LAST-MODIFIED', $lastModified);
+
+		return $fragment
+			.$this->buildICalLine('DTSTAMP', $dtStamp)
+			.$this->buildICalLine('END', 'VEVENT');
+	}
+
+	protected function buildCalendarCtag($userUID)
+	{
+		$data = $this->getCalendarData($userUID);
+		if(!is_array($data))
+			$data = array();
+
+		$fragments = array();
+		foreach($data as $row)
+		{
+			$lastModified = isset($row->updateamum) ? $this->getLastModifiedTimestamp($row->updateamum) : null;
+			$calendarData = isset($row->calendarDataFragment) ? $this->makeCal($row->calendarDataFragment) : '';
+			$fragments[] = $this->getObjectUri($row).':'.$lastModified.':'.md5($calendarData);
+		}
+
+		sort($fragments, SORT_STRING);
+		return 'LVPlan-'.$userUID.'-'.md5(implode('|', $fragments));
+	}
+
+	protected function buildICalTextLine($name, $value, array $parameters = array())
+	{
+		return $this->buildICalLine($name, $this->escapeICalText($value), $parameters);
+	}
+
+	protected function buildICalLine($name, $value, array $parameters = array())
+	{
+		$line = strtoupper($name);
+
+		foreach($parameters as $parameterName => $parameterValue)
+		{
+			$parameterValues = is_array($parameterValue) ? $parameterValue : array($parameterValue);
+			$escapedValues = array();
+
+			foreach($parameterValues as $singleParameterValue)
+				$escapedValues[] = $this->escapeICalParameterValue($singleParameterValue);
+
+			$line .= ';'.strtoupper($parameterName).'='.implode(',', $escapedValues);
+		}
+
+		return $this->foldICalLine($line.':'.(string)$value);
+	}
+
+	protected function foldICalLine($line)
+	{
+		$line = (string)$line;
+		$folded = '';
+
+		while(strlen($line) > 75)
+		{
+			$part = mb_strcut($line, 0, 75, 'UTF-8');
+			$folded .= $part."\r\n";
+			$line = ' '.mb_strcut($line, strlen($part), strlen($line) - strlen($part), 'UTF-8');
+		}
+
+		return $folded.$line."\r\n";
+	}
+
+	protected function escapeICalText($value)
+	{
+		$value = (string)$value;
+		$value = str_replace('\\', '\\\\', $value);
+		$value = str_replace(array("\r\n", "\r", "\n"), '\n', $value);
+		return str_replace(array(';', ','), array('\;', '\,'), $value);
+	}
+
+	protected function escapeICalParameterValue($value)
+	{
+		$value = (string)$value;
+		$value = str_replace(array('\\', '"', "\r", "\n"), array('\\\\', '\"', '', ''), $value);
+
+		if(preg_match('/[;:,]/', $value))
+			return '"'.$value.'"';
+
+		return $value;
+	}
+
+	protected function formatICalLocalDateTime($dateTime)
+	{
+		$dateTime = $this->createDateTime($dateTime);
+		if($dateTime === null)
+			return null;
+
+		$dateTime->setTimezone(new DateTimeZone('Europe/Vienna'));
+		return $dateTime->format('Ymd\THis');
+	}
+
+	protected function formatICalUtcDateTime($dateTime)
+	{
+		$dateTime = $this->createDateTime($dateTime);
+		if($dateTime === null)
+			return null;
+
+		$dateTime->setTimezone(new DateTimeZone('UTC'));
+		return $dateTime->format('Ymd\THis\Z');
+	}
+
+	protected function createDateTime($dateTime)
+	{
+		if($dateTime instanceof DateTime)
+			return clone $dateTime;
+
+		if($dateTime === null || $dateTime === '')
+			return null;
+
+		try
+		{
+			if(is_numeric($dateTime))
+				return new DateTime('@'.(int)$dateTime);
+
+			return new DateTime($dateTime);
+		}
+		catch(Exception $e)
+		{
+			return null;
+		}
+	}
+
+	protected function getObjectUri($row)
+	{
+		return md5($row->eindeutige_gruppen_id).'.ics';
+	}
+
+	protected function normalizeObjectUri($objectUri)
+	{
+		$normalizedObjectUri = (string)$objectUri;
+
+		if(substr($normalizedObjectUri, -4) === '.ics')
+			$normalizedObjectUri = substr($normalizedObjectUri, 0, -4);
+
+		if(mb_strpos($normalizedObjectUri, '@') !== false)
+			$normalizedObjectUri = mb_substr($normalizedObjectUri, mb_strpos($normalizedObjectUri, '@') + 1);
+
+		if($this->hasObjectUriDatePrefix($normalizedObjectUri))
+			return mb_substr($normalizedObjectUri, mb_strpos($normalizedObjectUri, '-') + 1);
+
+		return $normalizedObjectUri;
+	}
+
+	protected function hasObjectUriDatePrefix($objectUri)
+	{
+		$hyphenPosition = mb_strpos($objectUri, '-');
+		if($hyphenPosition !== 15)
+			return false;
+
+		return preg_match('/^\d{8}T\d{6}$/', mb_substr($objectUri, 0, 15)) === 1;
+	}
+
+	protected function buildCalendarObject($row, $calendarId)
+	{
+		$calendarData = $this->makeCal($row->calendarDataFragment);
+
+		return array(
+			"id"=>$row->eindeutige_gruppen_id,
+			"calendardata"=>$calendarData,
+			"uri"=>$this->getObjectUri($row),
+			"lastmodified"=>$this->getLastModifiedTimestamp($row->updateamum),
+			"etag"=>'"'.md5($calendarData).'"',
+			"calendarid"=>$calendarId,
+			"size"=>strlen($calendarData),
+			"component"=>'vevent'
+		);
+	}
+
+	protected function getLastModifiedTimestamp($lastModified)
+	{
+		if($lastModified === null || $lastModified === '')
+			return null;
+
+		if(is_numeric($lastModified))
+			return (int)$lastModified;
+
+		$timestamp = strtotime($lastModified);
+		if($timestamp === false)
+			return null;
+
+		return $timestamp;
+	}
+
+    /**
+     * Returns all calendar objects within a calendar.
+     *
+     * Every item contains an array with the following keys:
+     *   * id - unique identifier which will be used for subsequent updates
+     *   * calendardata - The iCalendar-compatible calnedar data
+     *   * uri - a unique key which will be used to construct the uri. This can be any arbitrary string.
+     *   * lastmodified - a timestamp of the last modification time
+     *   * etag - An arbitrary string, surrounded by double-quotes. (e.g.:
+     *   '  "abcdef"')
+     *   * calendarid - The calendarid as it was passed to this function.
+     *
+     * Note that the etag is optional, but it's highly encouraged to return for
+     * speed reasons.
+     *
+     * The calendardata is also optional. If it's not returned
+     * 'getCalendarObject' will be called later, which *is* expected to return
+     * calendardata.
+     *
+     * @param string $calendarId
+     * @return array
+     */
+    public function getCalendarObjects($calendarId)
+	{
+		//$user = $this->getUser();
+		$user = $calendarId;
+		$data = $this->getCalendarData($user);
+
+		//error_log("Caldav_Backend.php/getCalendarObjects($calendarId) ");
+		$return  = array();
+
+		if(!is_array($data))
+			return $return;
+
+		foreach($data as $row)
+		{
+			$return[] = $this->buildCalendarObject($row, $calendarId);
+		}
+		return $return;
+    }
+
+    /**
+     * Returns information from a single calendar object, based on it's object
+     * uri.
+     *
+     * The returned array must have the same keys as getCalendarObjects. The
+     * 'calendardata' object is required here though, while it's not required
+     * for getCalendarObjects.
+     *
+     * @param string $calendarId
+     * @param string $objectUri
+     * @return array
+     */
+    public function getCalendarObject($calendarId,$objectUri)
+	{
+		$user = $calendarId;
+		$data = $this->getCalendarData($user,$objectUri);
+
+		if(empty($data))
+		{
+			return null;
+		}
+		elseif(is_object($data))
+		{
+			$ret = $this->buildCalendarObject($data, $calendarId);
+		}
+
+		return isset($ret) ? $ret : null;
+    }
+
+    /**
+     * Creates a new calendar object.
+     *
+     * @param string $calendarId
+     * @param string $objectUri
+     * @param string $calendarData
+     * @return void
+     */
+    public function createCalendarObject($calendarId,$objectUri,$calendarData)
+	{
+		return null;
+    }
+
+    /**
+     * Updates an existing calendarobject, based on it's uri.
+     *
+     * @param string $calendarId
+     * @param string $objectUri
+     * @param string $calendarData
+     * @return void
+     */
+    public function updateCalendarObject($calendarId,$objectUri,$calendarData)
+	{
+		if(is_resource($calendarData))
+			$calendarData = stream_get_contents($calendarData);
+
+		return '"'.md5((string)$calendarData).'"';
+    }
+
+    /**
+     * Deletes an existing calendar object.
+     *
+     * @param string $calendarId
+     * @param string $objectUri
+     * @return void
+     */
+    public function deleteCalendarObject($calendarId,$objectUri)
+	{
+		return null;
+    }
+}
+
+/**
+ * Read-only CalDAV node wrappers for DB-owned calendars.
+ */
+class SabreDAVReadOnlyACLLib
+{
+	public static function getAcl($principalUri, $includeFreeBusy = false)
+	{
+		$acl = array(
+			array(
+				'privilege' => '{DAV:}read',
+				'principal' => $principalUri,
+				'protected' => true,
+			),
+			array(
+				'privilege' => '{DAV:}read',
+				'principal' => $principalUri.'/calendar-proxy-read',
+				'protected' => true,
+			),
+		);
+
+		if($includeFreeBusy)
+		{
+			$acl[] = array(
+				'privilege' => '{'.\Sabre\CalDAV\Plugin::NS_CALDAV.'}read-free-busy',
+				'principal' => '{DAV:}authenticated',
+				'protected' => true,
+			);
+		}
+
+		return $acl;
+	}
+
+	public static function ignoreWrite()
+	{
+		return null;
+	}
+}
+
+class SabreDAVReadOnlyCalendarRootLib extends \Sabre\CalDAV\CalendarRoot
+{
+	protected $readOnlyCaldavBackend;
+
+	public function __construct(\Sabre\DAVACL\PrincipalBackend\BackendInterface $principalBackend, \Sabre\CalDAV\Backend\BackendInterface $caldavBackend, $principalPrefix = 'principals')
+	{
+		parent::__construct($principalBackend, $caldavBackend, $principalPrefix);
+		$this->readOnlyCaldavBackend = $caldavBackend;
+	}
+
+	public function getChildForPrincipal(array $principal)
+	{
+		return new SabreDAVReadOnlyCalendarHomeLib($this->readOnlyCaldavBackend, $principal);
+	}
+}
+
+class SabreDAVReadOnlyCalendarHomeLib extends \Sabre\CalDAV\CalendarHome
+{
+	protected $readOnlyCaldavBackend;
+	protected $readOnlyPrincipalInfo;
+
+	public function __construct(\Sabre\CalDAV\Backend\BackendInterface $caldavBackend, $principalInfo)
+	{
+		parent::__construct($caldavBackend, $principalInfo);
+		$this->readOnlyCaldavBackend = $caldavBackend;
+		$this->readOnlyPrincipalInfo = $principalInfo;
+	}
+
+	public function getChildren()
+	{
+		$calendars = $this->readOnlyCaldavBackend->getCalendarsForUser($this->readOnlyPrincipalInfo['uri']);
+		$objs = array();
+
+		foreach($calendars as $calendar)
+		{
+			$objs[] = new SabreDAVReadOnlyCalendarLib($this->readOnlyCaldavBackend, $calendar);
+		}
+
+		return $objs;
+	}
+
+	public function createExtendedCollection($name, \Sabre\DAV\MkCol $mkCol)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function createFile($filename, $data = null)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function createDirectory($filename)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function delete()
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function setName($name)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function getACL()
+	{
+		return SabreDAVReadOnlyACLLib::getAcl($this->readOnlyPrincipalInfo['uri']);
+	}
+}
+
+class SabreDAVReadOnlyCalendarLib extends \Sabre\CalDAV\Calendar
+{
+	protected $readOnlyCaldavBackend;
+	protected $readOnlyCalendarInfo;
+
+	public function __construct(\Sabre\CalDAV\Backend\BackendInterface $caldavBackend, $calendarInfo)
+	{
+		parent::__construct($caldavBackend, $calendarInfo);
+		$this->readOnlyCaldavBackend = $caldavBackend;
+		$this->readOnlyCalendarInfo = $calendarInfo;
+	}
+
+	public function getChild($name)
+	{
+		$obj = $this->readOnlyCaldavBackend->getCalendarObject($this->readOnlyCalendarInfo['id'], $name);
+
+		if(!$obj)
+			throw new \Sabre\DAV\Exception\NotFound('Calendar object not found');
+
+		$obj['acl'] = $this->getCalendarObjectAcl();
+
+		return new SabreDAVReadOnlyCalendarObjectLib($this->readOnlyCaldavBackend, $this->readOnlyCalendarInfo, $obj);
+	}
+
+	public function getChildren()
+	{
+		$objs = $this->readOnlyCaldavBackend->getCalendarObjects($this->readOnlyCalendarInfo['id']);
+		$children = array();
+
+		foreach($objs as $obj)
+		{
+			$obj['acl'] = $this->getCalendarObjectAcl();
+			$children[] = new SabreDAVReadOnlyCalendarObjectLib($this->readOnlyCaldavBackend, $this->readOnlyCalendarInfo, $obj);
+		}
+
+		return $children;
+	}
+
+	public function createFile($name, $calendarData = null)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function createDirectory($name)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function delete()
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function setName($newName)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function updateProperties($mutations)
+	{
+		return true;
+	}
+
+	public function propPatch(\Sabre\DAV\PropPatch $propPatch)
+	{
+		$propPatch->setRemainingResultCode(200);
+	}
+
+	public function getACL()
+	{
+		return SabreDAVReadOnlyACLLib::getAcl($this->getOwner(), true);
+	}
+
+	protected function getCalendarObjectAcl()
+	{
+		return SabreDAVReadOnlyACLLib::getAcl($this->getOwner());
+	}
+}
+
+class SabreDAVReadOnlyCalendarObjectLib extends \Sabre\CalDAV\CalendarObject
+{
+	protected $readOnlyCalendarInfo;
+
+	public function __construct(\Sabre\CalDAV\Backend\BackendInterface $caldavBackend, array $calendarInfo, array $objectData)
+	{
+		parent::__construct($caldavBackend, $calendarInfo, $objectData);
+		$this->readOnlyCalendarInfo = $calendarInfo;
+	}
+
+	public function put($calendarData)
+	{
+		return $this->getETag();
+	}
+
+	public function getETag()
+	{
+		if(isset($_SERVER['REQUEST_METHOD']) && in_array($_SERVER['REQUEST_METHOD'], array('PUT', 'DELETE'), true))
+		{
+			$ifMatch = isset($_SERVER['HTTP_IF_MATCH']) ? trim($_SERVER['HTTP_IF_MATCH']) : '';
+			if($ifMatch !== '' && $ifMatch !== '*')
+			{
+				$requestedEtags = explode(',', $ifMatch);
+				foreach($requestedEtags as $requestedEtag)
+				{
+					$requestedEtag = trim($requestedEtag);
+					if($requestedEtag !== '')
+						return $requestedEtag;
+				}
+			}
+		}
+
+		return parent::getETag();
+	}
+
+	public function delete()
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function setName($name)
+	{
+		return SabreDAVReadOnlyACLLib::ignoreWrite();
+	}
+
+	public function getACL()
+	{
+		return SabreDAVReadOnlyACLLib::getAcl($this->readOnlyCalendarInfo['principaluri']);
+	}
+}