diff --git a/generator/generator.php b/generator/generator.php
index 78f02b3..d6413c0 100755
--- a/generator/generator.php
+++ b/generator/generator.php
@@ -7,47 +7,79 @@ foreach (getenv() as $k => $v) {
     $search[] = "\$$k";
     $replace[] = '"' . addslashes($v) . '"';
 }
-$conf = yaml_parse(str_replace($search, $replace, file_get_contents(__DIR__ . '/config.yaml')));
+$conf = yaml_parse(
+    str_replace($search, $replace, file_get_contents(__DIR__ . "/config.yaml"))
+);
 $c = new \Mosquitto\Client();
-if (isset($conf['mqtt']['user'])) $c->setCredentials($conf['mqtt']['user'], $conf['mqtt']['password']);
+if (isset($conf["mqtt"]["user"])) {
+    $c->setCredentials($conf["mqtt"]["user"], $conf["mqtt"]["password"]);
+}
 $c->onMessage(function (\Mosquitto\Message $message) use (&$data, $conf) {
-    if (!isset($data[$message->topic])) return;
+    if (!isset($data[$message->topic])) {
+        return;
+    }
 
-    switch ($data[$message->topic]['cast']) {
-        case 'int':
-            $data[$message->topic]['value'] = (int)$message->payload;
+    switch ($data[$message->topic]["cast"]) {
+        case "int":
+            $data[$message->topic]["value"] = (int) $message->payload;
             break;
-        case 'float':
-            $data[$message->topic]['value'] = (float)$message->payload;
+        case "float":
+            $data[$message->topic]["value"] = (float) $message->payload;
             break;
-        case 'bool':
-            $data[$message->topic]['value'] = (bool)$message->payload;
+        case "bool":
+            $data[$message->topic]["value"] = (bool) $message->payload;
             break;
         default:
-            echo "error, cast type " . $data[$message->topic]['cast'] . " unknown\n";
+            echo "error, cast type " .
+                $data[$message->topic]["cast"] .
+                " unknown\n";
             die(1);
     }
-    $search = [];
-    $replace = [];
-    foreach ($data as $v) {
-        $search[] = '"{{' . $v['name'] . '}}"';
-        $replace[] = json_encode($v['value']);
+    $data[$message->topic]["changed"] = time();
+    $out = file_get_contents(__DIR__ . "/template.json");
+    $out = preg_replace_callback(
+        "/{{(?<name>[^#}]+?)(#(?<modifier>[^}]+))?}}/",
+        function ($m) use ($data, $conf) {
+            $value = $data[$conf["variables"][$m["name"]]["topic"]]["value"];
+            $modifier = isset($m["modifier"]) ? $m["modifier"] : "noop";
+            switch ($modifier) {
+                case "timestamp":
+                    $value =
+                        $data[$conf["variables"][$m["name"]]["topic"]][
+                            "changed"
+                        ];
+                    break;
+                case "noop":
+                    break;
+
+                default:
+                    echo "error, modifier " . $m["modifier"] . " unknown\n";
+                    die(1);
+            }
+            return json_encode($value);
+        },
+        $out
+    );
+
+    $out = json_encode(
+        json_decode($out),
+        JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE
+    );
+    if (!is_dir("public")) {
+        mkdir("public");
     }
-
-    $out = str_replace($search, $replace, file_get_contents(__DIR__ . '/template.json'));
-    $out = json_encode(json_decode($out), JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
-    if (!is_dir('public')) mkdir('public');
-    file_put_contents('public/spaceapi.json', $out);
+    file_put_contents("public/spaceapi.json", $out);
 });
-$c->connect($conf['mqtt']['host']);
+$c->connect($conf["mqtt"]["host"]);
 $data = [];
-foreach ($conf['variables'] as $name => $variable) {
-    $data[$variable['topic']] = [
-
-        'value' => null,
-        'cast' => $variable['cast'],
-        'name' => $name
+foreach ($conf["variables"] as $name => $variable) {
+    $data[$variable["topic"]] = [
+        "value" => null,
+        "cast" => $variable["cast"],
+        "name" => $name,
+        "changed" => 0,
     ];
-    $c->subscribe($variable['topic'], 2);
+    $c->subscribe($variable["topic"], 2);
 }
-$c->loopForever();
\ No newline at end of file
+$c->loopForever();
+
diff --git a/generator/template.json b/generator/template.json
index d0e1b9b..dbe41d5 100644
--- a/generator/template.json
+++ b/generator/template.json
@@ -1,44 +1,40 @@
 {
-    "api":"0.13",
-    "space":"Chaostreff Recklinghausen c3RE",
-    "logo":"https://c3re.de/wp-content/uploads/logo/Logo_weiss_rund_schwarzer_Rand.png",
-    "url":"https://c3re.de",
-    "location":{
-        "address":"Westcharweg 101, 45659 Recklinghausen",
-        "lon":7.1690101828426,
-        "lat":51.62435592244
-    },
-    "contact":{
-        "twitter":"@c3_re",
-        "email":"kontakt@c3RE.de",
-        "issue_mail":"kontakt@c3RE.de"
-        },
-    "issue_report_channels":[
-        "email"
-    ],
-    "state":{
-        "open": "{{doorstatus}}",
-        "icon": {
-            "open":"https://c3re.de/doorstatus/open.png",
-            "closed":"https://c3re.de/doorstatus/closed.png"
-        }
-    },
-    "sensors": {
-   	 "temperature": [
-     	 {
-       	 	"location": "Clubraum",
-        	"unit": "°C",
-        	"value": "{{clubraum_temp}}"
-      	},
-      	{
-        	"location": "Werkstatt",
-        	"unit": "°C",
-        	"value": "{{werkstatt_temp}}"
-      	}
-    	]
-    },
-    "projects":[
-        "https://github.com/c3re",
-        "https://git.c3re.de"
-        ]
+  "api": "0.13",
+  "space": "Chaostreff Recklinghausen c3RE",
+  "logo": "https://c3re.de/wp-content/uploads/logo/Logo_weiss_rund_schwarzer_Rand.png",
+  "url": "https://c3re.de",
+  "location": {
+    "address": "Westcharweg 101, 45659 Recklinghausen",
+    "lon": 7.1690101828426,
+    "lat": 51.62435592244
+  },
+  "contact": {
+    "twitter": "@c3_re",
+    "email": "kontakt@c3RE.de",
+    "issue_mail": "kontakt@c3RE.de"
+  },
+  "issue_report_channels": ["email"],
+  "state": {
+    "open": "{{doorstatus}}",
+    "lastchange": "{{doorstatus#timestamp}}",
+    "icon": {
+      "open": "https://c3re.de/doorstatus/open.png",
+      "closed": "https://c3re.de/doorstatus/closed.png"
+    }
+  },
+  "sensors": {
+    "temperature": [
+      {
+        "location": "Clubraum",
+        "unit": "°C",
+        "value": "{{clubraum_temp}}"
+      },
+      {
+        "location": "Werkstatt",
+        "unit": "°C",
+        "value": "{{werkstatt_temp}}"
+      }
+    ]
+  },
+  "projects": ["https://github.com/c3re", "https://git.c3re.de"]
 }