diff --git a/Core/Distrib.php b/Core/Distrib.php
index 157b8f0..ebd9c76 100644
--- a/Core/Distrib.php
+++ b/Core/Distrib.php
@@ -24,5 +24,5 @@
 #  This copyright notice MUST APPEAR in all copies of the script!
 #################################################################
 
-define("BAIKAL_VERSION", "0.5.0");
+define("BAIKAL_VERSION", "0.5.1");
 define("BAIKAL_HOMEPAGE", "http://sabre.io/baikal/");
diff --git a/Core/Frameworks/Baikal/Model/Calendar.php b/Core/Frameworks/Baikal/Model/Calendar.php
index 9634655..0d22b32 100644
--- a/Core/Frameworks/Baikal/Model/Calendar.php
+++ b/Core/Frameworks/Baikal/Model/Calendar.php
@@ -28,7 +28,7 @@
 namespace Baikal\Model;
 
 class Calendar extends \Flake\Core\Model\Db {
-    const DATATABLE = "calendars";
+    const DATATABLE = "calendarinstances";
     const PRIMARYKEY = "id";
     const LABELFIELD = "displayname";
 
@@ -40,8 +40,25 @@ class Calendar extends \Flake\Core\Model\Db {
         "calendarorder" => 0,
         "calendarcolor" => "",
         "timezone"      => "",
-        "components"    => "",
+        "calendarid"    => 0
     ];
+    protected $oCalendar; # Baikal\Model\Calendar\Calendar
+
+    protected function initFloating() {
+        parent::initFloating();
+        $this->oCalendar = new Calendar\Calendar();
+    }
+
+    protected function initByPrimary($sPrimary) {
+        parent::initByPrimary($sPrimary);
+        $this->oCalendar = new Calendar\Calendar($this->get("calendarid"));
+    }
+
+    function persist() {
+        $this->oCalendar->persist();
+        $this->aData["calendarid"] = $this->oCalendar->get("id");
+        parent::persist();
+    }
 
     static function icon() {
         return "icon-calendar";
@@ -67,6 +84,10 @@ class Calendar extends \Flake\Core\Model\Db {
 
     function get($sPropName) {
 
+        if ($sPropName === "components") {
+            return $this->oCalendar->get($sPropName);
+        }
+
         if ($sPropName === "todos") {
             # TRUE if components contains VTODO, FALSE otherwise
             if (($sComponents = $this->get("components")) !== "") {
@@ -94,6 +115,10 @@ class Calendar extends \Flake\Core\Model\Db {
 
     function set($sPropName, $sValue) {
 
+        if ($sPropName === "components") {
+            return $this->oCalendar->set($sPropName, $sValue);
+        }
+
         if ($sPropName === "todos") {
 
             if (($sComponents = $this->get("components")) !== "") {
@@ -112,7 +137,7 @@ class Calendar extends \Flake\Core\Model\Db {
                 }
             }
 
-            return parent::set("components", implode(",", $aComponents));
+            return $this->set("components", implode(",", $aComponents));
         }
 
         if ($sPropName === "notes") {
@@ -133,7 +158,7 @@ class Calendar extends \Flake\Core\Model\Db {
                 }
             }
 
-            return parent::set("components", implode(",", $aComponents));
+            return $this->set("components", implode(",", $aComponents));
         }
 
         return parent::set($sPropName, $sValue);
@@ -215,5 +240,6 @@ class Calendar extends \Flake\Core\Model\Db {
         }
 
         parent::destroy();
+        $this->oCalendar->destroy();
     }
 }
diff --git a/Core/Frameworks/Baikal/Model/Calendar/Calendar.php b/Core/Frameworks/Baikal/Model/Calendar/Calendar.php
new file mode 100644
index 0000000..a92b775
--- /dev/null
+++ b/Core/Frameworks/Baikal/Model/Calendar/Calendar.php
@@ -0,0 +1,60 @@
+<?php
+#################################################################
+#  Copyright notice
+#
+#  (c) 2013 Jérôme Schneider <mail@jeromeschneider.fr>
+#  All rights reserved
+#
+#  http://baikal-server.com
+#
+#  This script is part of the Baïkal Server project. The Baïkal
+#  Server project is free software; you can redistribute it
+#  and/or modify it under the terms of the GNU General Public
+#  License as published by the Free Software Foundation; either
+#  version 2 of the License, or (at your option) any later version.
+#
+#  The GNU General Public License can be found at
+#  http://www.gnu.org/copyleft/gpl.html.
+#
+#  This script 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 General Public License for more details.
+#
+#  This copyright notice MUST APPEAR in all copies of the script!
+#################################################################
+
+
+namespace Baikal\Model\Calendar;
+
+class Calendar extends \Flake\Core\Model\Db {
+    const DATATABLE = "calendars";
+    const PRIMARYKEY = "id";
+    const LABELFIELD = "components";
+
+    protected $aData = [
+        "synctoken"  => "",
+        "components" => ""
+    ];
+
+    function hasInstances() {
+        $rSql = $GLOBALS["DB"]->exec_SELECTquery(
+            "*",
+            "calendarinstances",
+            "calendarid" . "='" . $this->aData["id"] . "'"
+        );
+
+        if (($aRs = $rSql->fetch()) === false) {
+            return false;
+        } else {
+            reset($aRs);
+            return true;
+        }
+    }
+
+    function destroy() {
+        if (!$this->hasInstances()) {
+            parent::destroy();
+        }
+    }
+}
diff --git a/Core/Frameworks/BaikalAdmin/Controller/Install/VersionUpgrade.php b/Core/Frameworks/BaikalAdmin/Controller/Install/VersionUpgrade.php
index 2783bda..7ac1b2c 100644
--- a/Core/Frameworks/BaikalAdmin/Controller/Install/VersionUpgrade.php
+++ b/Core/Frameworks/BaikalAdmin/Controller/Install/VersionUpgrade.php
@@ -377,6 +377,141 @@ CREATE TABLE addressbooks (
             }
 
         }
+        if (version_compare($sVersionFrom, '0.5.1', '<')) {
+            if (!defined("PROJECT_DB_MYSQL") || PROJECT_DB_MYSQL === false) {
+                $pdo->exec(<<<SQL
+CREATE TABLE calendarinstances (
+    id integer primary key asc NOT NULL,
+    calendarid integer,
+    principaluri text,
+    access integer COMMENT '1 = owner, 2 = read, 3 = readwrite' NOT NULL DEFAULT '1',
+    displayname text,
+    uri text NOT NULL,
+    description text,
+    calendarorder integer,
+    calendarcolor text,
+    timezone text,
+    transparent bool,
+    share_href text,
+    share_displayname text,
+    share_invitestatus integer DEFAULT '2',
+    UNIQUE (principaluri, uri),
+    UNIQUE (calendarid, principaluri),
+    UNIQUE (calendarid, share_href)
+);
+SQL
+        );
+                $this->aSuccess[] = 'Created calendarinstances table';
+                $pdo->exec('
+INSERT INTO calendarinstances
+    (
+        calendarid,
+        principaluri,
+        access,
+        displayname,
+        uri,
+        description,
+        calendarorder,
+        calendarcolor,
+        transparent
+    )
+SELECT
+    id,
+    principaluri,
+    1,
+    displayname,
+    uri,
+    description,
+    calendarorder,
+    calendarcolor,
+    transparent
+FROM calendars
+');
+                $this->aSuccess[] = 'Migrated calendarinstances table';
+                $calendarBackup = 'calendars_3_1';
+                $pdo->exec('ALTER TABLE calendars RENAME TO ' . $calendarBackup);
+                $this->aSuccess[] = 'Did calendars backup';
+
+                $pdo->exec(<<<SQL
+CREATE TABLE calendars (
+    id integer primary key asc NOT NULL,
+    synctoken integer DEFAULT 1 NOT NULL,
+    components text NOT NULL
+);
+SQL
+        );
+                $this->aSuccess[] = 'Created new calendars table';
+            } else { // mysql
+                $pdo->exec(<<<SQL
+CREATE TABLE calendarinstances (
+    id INTEGER UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT,
+    calendarid INTEGER UNSIGNED NOT NULL,
+    principaluri VARBINARY(100),
+    access TINYINT(1) NOT NULL DEFAULT '1' COMMENT '1 = owner, 2 = read, 3 = readwrite',
+    displayname VARCHAR(100),
+    uri VARBINARY(200),
+    description TEXT,
+    calendarorder INT(11) UNSIGNED NOT NULL DEFAULT '0',
+    calendarcolor VARBINARY(10),
+    timezone TEXT,
+    transparent TINYINT(1) NOT NULL DEFAULT '0',
+    share_href VARBINARY(100),
+    share_displayname VARCHAR(100),
+    share_invitestatus TINYINT(1) NOT NULL DEFAULT '2' COMMENT '1 = noresponse, 2 = accepted, 3 = declined, 4 = invalid',
+    UNIQUE(principaluri, uri),
+    UNIQUE(calendarid, principaluri),
+    UNIQUE(calendarid, share_href)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+SQL
+        );
+                $this->aSuccess[] = 'Created calendarinstances table';
+                $pdo->exec('
+INSERT INTO calendarinstances
+    (
+        calendarid,
+        principaluri,
+        access,
+        displayname,
+        uri,
+        description,
+        calendarorder,
+        calendarcolor,
+        transparent
+    )
+SELECT
+    id,
+    principaluri,
+    1,
+    displayname,
+    uri,
+    description,
+    calendarorder,
+    calendarcolor,
+    transparent
+FROM calendars
+');
+                $this->aSuccess[] = 'Migrated calendarinstances table';
+                $calendarBackup = 'calendars_3_1';
+                $pdo->exec('RENAME TABLE calendars TO ' . $calendarBackup);
+                $this->aSuccess[] = 'Did calendars backup';
+
+                $pdo->exec(<<<SQL
+CREATE TABLE calendars (
+    id INTEGER UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT,
+    synctoken INTEGER UNSIGNED NOT NULL DEFAULT '1',
+    components VARBINARY(21)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
+SQL
+);
+                $this->aSuccess[] = 'Created new calendars table';
+            }
+
+            $pdo->exec(<<<SQL
+INSERT INTO calendars (id, synctoken, components) SELECT id, synctoken, COALESCE(components,"VEVENT,VTODO,VJOURNAL") as components FROM $calendarBackup
+SQL
+    );
+            $this->aSuccess[] = 'Migrated calendars table';
+        }
 
 
         $this->updateConfiguredVersion($sVersionTo);
diff --git a/Core/Resources/Db/MySQL/db.sql b/Core/Resources/Db/MySQL/db.sql
index 6dc4e23..e572c5b 100644
--- a/Core/Resources/Db/MySQL/db.sql
+++ b/Core/Resources/Db/MySQL/db.sql
@@ -26,6 +26,7 @@ CREATE TABLE addressbookchanges (
     operation TINYINT(1) NOT NULL,
     INDEX addressbookid_synctoken (addressbookid, synctoken)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
 CREATE TABLE calendarobjects (
     id INT(11) UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT,
     calendardata MEDIUMBLOB,
@@ -43,17 +44,28 @@ CREATE TABLE calendarobjects (
 
 CREATE TABLE calendars (
     id INTEGER UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT,
+    synctoken INTEGER UNSIGNED NOT NULL DEFAULT '1',
+    components VARBINARY(21)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
+
+CREATE TABLE calendarinstances (
+    id INTEGER UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT,
+    calendarid INTEGER UNSIGNED NOT NULL,
     principaluri VARBINARY(100),
+    access TINYINT(1) NOT NULL DEFAULT '1',
     displayname VARCHAR(100),
     uri VARBINARY(200),
-    synctoken INTEGER UNSIGNED NOT NULL DEFAULT '1',
     description TEXT,
     calendarorder INT(11) UNSIGNED NOT NULL DEFAULT '0',
     calendarcolor VARBINARY(10),
     timezone TEXT,
-    components VARBINARY(21),
     transparent TINYINT(1) NOT NULL DEFAULT '0',
-    UNIQUE(principaluri, uri)
+    share_href VARBINARY(100),
+    share_displayname VARCHAR(100),
+    share_invitestatus TINYINT(1) NOT NULL DEFAULT '2',
+    UNIQUE(principaluri, uri),
+    UNIQUE(calendarid, principaluri),
+    UNIQUE(calendarid, share_href)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 
 CREATE TABLE calendarchanges (
diff --git a/Core/Resources/Db/SQLite/db.sql b/Core/Resources/Db/SQLite/db.sql
index e8b8d55..6d3bf7c 100644
--- a/Core/Resources/Db/SQLite/db.sql
+++ b/Core/Resources/Db/SQLite/db.sql
@@ -42,16 +42,28 @@ CREATE TABLE calendarobjects (
 
 CREATE TABLE calendars (
     id integer primary key asc NOT NULL,
-    principaluri text NOT NULL,
+    synctoken integer DEFAULT 1 NOT NULL,
+    components text NOT NULL
+);
+
+CREATE TABLE calendarinstances (
+    id integer primary key asc NOT NULL,
+    calendarid integer,
+    principaluri text,
+    access integer,
     displayname text,
     uri text NOT NULL,
-    synctoken integer DEFAULT 1 NOT NULL,
     description text,
     calendarorder integer,
     calendarcolor text,
     timezone text,
-    components text NOT NULL,
-    transparent bool
+    transparent bool,
+    share_href text,
+    share_displayname text,
+    share_invitestatus integer DEFAULT '2',
+    UNIQUE (principaluri, uri),
+    UNIQUE (calendarid, principaluri),
+    UNIQUE (calendarid, share_href)
 );
 
 CREATE TABLE calendarchanges (
diff --git a/composer.json b/composer.json
index dc35613..8c2d1ba 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
     ],
     "require": {
         "php"           : ">=5.5",
-        "sabre/dav"     : "~3.1.2",
+        "sabre/dav"     : "~3.2.3",
         "twig/twig"     : "~1.8.0"
     },
     "require-dev" : {