diff --git a/src/shared/services/mqttSubscriber.ts b/src/shared/services/mqttSubscriber.ts
index aec5de4..e0c1f87 100644
--- a/src/shared/services/mqttSubscriber.ts
+++ b/src/shared/services/mqttSubscriber.ts
@@ -92,12 +92,14 @@ function parseDeviceTime(value: unknown) {
     return new Date().toISOString();
   }
 
+  // QF100 firmware sends NTP-local WIB time (UTC+7) in YYYYMMDDHHMMSS.
+  // Store timestamps in UTC so heartbeat age and last-seen calculations stay correct.
   const parsed = new Date(
     Date.UTC(
       Number(match[1]),
       Number(match[2]) - 1,
       Number(match[3]),
-      Number(match[4]),
+      Number(match[4]) - 7,
       Number(match[5]),
       Number(match[6])
     )