diff --git a/homeassistant/components/ios.py b/homeassistant/components/ios.py
index cfa1693f571..ebabcdb0e79 100644
--- a/homeassistant/components/ios.py
+++ b/homeassistant/components/ios.py
@@ -264,7 +264,7 @@ class iOSIdentifyDeviceView(HomeAssistantView):
         #     return self.json_message(humanize_error(request.json, ex),
         #                              HTTP_BAD_REQUEST)
 
-        data[ATTR_LAST_SEEN_AT] = datetime.datetime.now()
+        data[ATTR_LAST_SEEN_AT] = datetime.datetime.now().isoformat()
 
         name = data.get(ATTR_DEVICE_ID)