diff --git a/AddOn/.DS_Store b/AddOn/.DS_Store
new file mode 100644
index 00000000..99e69f7d
Binary files /dev/null and b/AddOn/.DS_Store differ
diff --git a/AddOn/Calender_Office365_User/OutlookCalendar.php b/AddOn/Calender_Office365_User/OutlookCalendar.php
new file mode 100644
index 00000000..c0661afe
--- /dev/null
+++ b/AddOn/Calender_Office365_User/OutlookCalendar.php
@@ -0,0 +1,102 @@
+<?php
+
+class OutlookCalendar {
+    private $clientId;
+    private $clientSecret;
+    private $redirectUri;
+    private $accessToken;
+    private $refreshToken;
+
+    public function __construct($clientId, $clientSecret, $redirectUri, $accessToken, $refreshToken) {
+        $this->clientId     = $clientId;
+        $this->clientSecret = $clientSecret;
+        $this->redirectUri  = $redirectUri;
+        $this->accessToken  = $accessToken;
+        $this->refreshToken = $refreshToken;
+    }
+
+    // ------------------------------------------
+    // 🔁 Refresh Token verwenden
+    public function refreshAccessToken() {
+        $url = "https://login.microsoftonline.com/common/oauth2/v2.0/token";
+
+        $data = [
+            'grant_type'    => 'refresh_token',
+            'refresh_token' => $this->refreshToken,
+            'client_id'     => $this->clientId,
+            'client_secret' => $this->clientSecret,
+            'redirect_uri'  => $this->redirectUri,
+            'scope'         => 'https://graph.microsoft.com/.default'
+        ];
+
+        $response = $this->sendRequest($url, $data, true);
+        if (isset($response['access_token'])) {
+            $this->accessToken = $response['access_token'];
+            $this->refreshToken = $response['refresh_token'] ?? $this->refreshToken;
+        }
+
+        return $response;
+    }
+
+    // ------------------------------------------
+    // 📅 Termin erstellen
+    public function createEvent($eventData) {
+        $url = "https://graph.microsoft.com/v1.0/me/events";
+        return $this->sendRequest($url, $eventData, false, 'POST');
+    }
+
+    // ✏️ Termin bearbeiten
+    public function updateEvent($eventId, $eventData) {
+        $url = "https://graph.microsoft.com/v1.0/me/events/{$eventId}";
+        return $this->sendRequest($url, $eventData, false, 'PATCH');
+    }
+
+    // ❌ Termin löschen
+    public function deleteEvent($eventId) {
+        $url = "https://graph.microsoft.com/v1.0/me/events/{$eventId}";
+        return $this->sendRequest($url, [], false, 'DELETE');
+    }
+
+    // ------------------------------------------
+    // 🔧 API Request senden (intern)
+    private function sendRequest($url, $data = [], $isForm = false, $method = 'POST') {
+        $ch = curl_init($url);
+        $headers = [
+            'Authorization: Bearer ' . $this->accessToken,
+        ];
+
+        if ($isForm) {
+            $body = http_build_query($data);
+            $headers[] = 'Content-Type: application/x-www-form-urlencoded';
+        } else {
+            $body = json_encode($data);
+            $headers[] = 'Content-Type: application/json';
+        }
+
+        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+        curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $method);
+        if ($method !== 'GET' && !empty($data)) {
+            curl_setopt($ch, CURLOPT_POSTFIELDS, $body);
+        }
+        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
+
+        $response = curl_exec($ch);
+        $err = curl_error($ch);
+        curl_close($ch);
+
+        if ($err) {
+            return ['error' => $err];
+        }
+
+        return json_decode($response, true);
+    }
+
+    // 🔓 Getter für AccessToken
+    public function getAccessToken() {
+        return $this->accessToken;
+    }
+
+    public function getRefreshToken() {
+        return $this->refreshToken;
+    }
+}
diff --git a/AddOn/Calender_Office365_User/auth.php b/AddOn/Calender_Office365_User/auth.php
new file mode 100644
index 00000000..6b8814cd
--- /dev/null
+++ b/AddOn/Calender_Office365_User/auth.php
@@ -0,0 +1,14 @@
+<?php
+$config = require 'config.php';
+
+$params = [
+    'client_id'     => $config['client_id'],
+    'response_type' => 'code',
+    'redirect_uri'  => $config['redirect_uri'],
+    'response_mode' => 'query',
+    'scope'         => $config['scopes'],
+];
+
+$authUrl = $config['auth_url'] . '?' . http_build_query($params);
+header("Location: $authUrl");
+exit;
diff --git a/AddOn/Calender_Office365_User/calendar.php b/AddOn/Calender_Office365_User/calendar.php
new file mode 100644
index 00000000..e7216c17
--- /dev/null
+++ b/AddOn/Calender_Office365_User/calendar.php
@@ -0,0 +1,56 @@
+<?php
+require 'OutlookCalendar.php';
+$config = require 'config.php';
+
+$email = $_GET['email'] ?? null;
+
+if (!$email || !file_exists($config['token_storage'])) {
+    die("Bitte logge dich zuerst über auth.php ein.");
+}
+
+$tokens = json_decode(file_get_contents($config['token_storage']), true);
+if (!isset($tokens[$email])) {
+    die("Kein Token für diese E-Mail gefunden.");
+}
+
+$data = $tokens[$email];
+
+$calendar = new OutlookCalendar(
+    $config['client_id'],
+    $config['client_secret'],
+    $config['redirect_uri'],
+    $data['access_token'],
+    $data['refresh_token']
+);
+
+// Optional: Token auffrischen, wenn abgelaufen
+if (time() > ($data['time_saved'] + $data['expires_in'] - 60)) {
+    $calendar->refreshAccessToken();
+    $tokens[$email]['access_token'] = $calendar->getAccessToken();
+    $tokens[$email]['refresh_token'] = $calendar->getRefreshToken();
+    $tokens[$email]['time_saved'] = time();
+    file_put_contents($config['token_storage'], json_encode($tokens, JSON_PRETTY_PRINT));
+}
+
+// ➤ Beispiel: Termin anlegen
+$event = [
+    "subject" => "Test-Meeting via PHP",
+    "start" => [
+        "dateTime" => "2025-06-25T10:00:00",
+        "timeZone" => "Europe/Berlin"
+    ],
+    "end" => [
+        "dateTime" => "2025-06-25T11:00:00",
+        "timeZone" => "Europe/Berlin"
+    ],
+    "body" => [
+        "contentType" => "HTML",
+        "content" => "Meeting von OutlookCalendar PHP"
+    ]
+];
+
+$response = $calendar->createEvent($event);
+
+echo "<pre>";
+print_r($response);
+echo "</pre>";
diff --git a/AddOn/Calender_Office365_User/callback.php b/AddOn/Calender_Office365_User/callback.php
new file mode 100644
index 00000000..11598156
--- /dev/null
+++ b/AddOn/Calender_Office365_User/callback.php
@@ -0,0 +1,69 @@
+<?php
+$config = require 'config.php';
+
+if (!isset($_GET['code'])) {
+    die("Authorization code fehlt.");
+}
+
+$code = $_GET['code'];
+
+// ➤ Token anfordern
+$data = [
+    'client_id'     => $config['client_id'],
+    'scope'         => $config['scopes'],
+    'code'          => $code,
+    'redirect_uri'  => $config['redirect_uri'],
+    'grant_type'    => 'authorization_code',
+    'client_secret' => $config['client_secret'],
+];
+
+$ch = curl_init($config['token_url']);
+curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));
+curl_setopt($ch, CURLOPT_POST, true);
+curl_setopt($ch, CURLOPT_HTTPHEADER, [
+    'Content-Type: application/x-www-form-urlencoded',
+]);
+
+$response = curl_exec($ch);
+curl_close($ch);
+
+$tokenData = json_decode($response, true);
+
+if (!isset($tokenData['access_token'])) {
+    die("Fehler beim Token-Abruf: " . $response);
+}
+
+// ➤ E-Mail-Adresse vom User holen
+$ch = curl_init($config['graph_url'] . '/me');
+curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+curl_setopt($ch, CURLOPT_HTTPHEADER, [
+    'Authorization: Bearer ' . $tokenData['access_token'],
+]);
+$userResponse = curl_exec($ch);
+curl_close($ch);
+
+$userData = json_decode($userResponse, true);
+$email = $userData['mail'] ?? $userData['userPrincipalName'] ?? null;
+
+if (!$email) {
+    die("Fehler beim Abrufen der E-Mail.");
+}
+
+// ➤ Speichern in tokens.json
+$tokens = [];
+if (file_exists($config['token_storage'])) {
+    $tokens = json_decode(file_get_contents($config['token_storage']), true);
+}
+
+$tokens[$email] = [
+    'access_token'  => $tokenData['access_token'],
+    'refresh_token' => $tokenData['refresh_token'],
+    'expires_in'    => $tokenData['expires_in'],
+    'time_saved'    => time()
+];
+
+file_put_contents($config['token_storage'], json_encode($tokens, JSON_PRETTY_PRINT));
+
+echo "Erfolgreich verbunden mit: <b>$email</b><br>";
+echo "<a href='calendar.php?email=" . urlencode($email) . "'>Zum Kalender-Tool</a>";
diff --git a/AddOn/Calender_Office365_User/config.php b/AddOn/Calender_Office365_User/config.php
new file mode 100644
index 00000000..5003cd24
--- /dev/null
+++ b/AddOn/Calender_Office365_User/config.php
@@ -0,0 +1,11 @@
+<?php
+return [
+    'client_id' => '<Application ID (Client ID)>',
+    'client_secret' => '<Cleint Secret Geheimnise / Zertifikate Wert>',
+    'redirect_uri' => 'https://servicebericht.isgus.de/calsync/callback.php',
+    'scopes' => 'offline_access user.read calendars.readwrite',
+    'auth_url' => 'https://login.microsoftonline.com/common/oauth2/v2.0/authorize',
+    'token_url' => 'https://login.microsoftonline.com/common/oauth2/v2.0/token',
+    'graph_url' => 'https://graph.microsoft.com/v1.0',
+    'token_storage' => __DIR__ . '/tokens.json',
+];