diff --git a/custom_components/audiconnect/dashboard.py b/custom_components/audiconnect/dashboard.py
index 61e61ea0..b63b3b21 100644
--- a/custom_components/audiconnect/dashboard.py
+++ b/custom_components/audiconnect/dashboard.py
@@ -2,7 +2,6 @@
 
 import logging
 import re
-from datetime import datetime
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -128,6 +127,7 @@ def attributes(self):
 class Sensor(Instrument):
     def __init__(self, attr, name, icon, unit):
         super().__init__(component="sensor", attr=attr, name=name, icon=icon)
+        self.device_class = None
         self._unit = unit
         self._convert = False
 
@@ -319,6 +319,7 @@ def str_state(self):
 class TripData(Instrument):
     def __init__(self, attr, name):
         super().__init__(component="sensor", attr=attr, name=name)
+        self.device_class = None
         self.unit = None
 
     @property
@@ -361,6 +362,7 @@ def __init__(self):
             name="Last Update",
             icon="mdi:update",
         )
+        self.device_class = "timestamp"
         self.unit = None
 
     @property
@@ -370,14 +372,12 @@ def is_mutable(self):
     @property
     def str_state(self):
         ts = super().state
-        if type(ts) == datetime:
-            return str(ts.astimezone(tz=None)) if ts else None
-        return ts
+        return ts.astimezone(tz=None).isoformat() if ts else None
 
     @property
     def state(self):
         val = super().state
-        return val
+        return val.astimezone(tz=None).isoformat() if val else None
 
 
 def create_instruments():
diff --git a/custom_components/audiconnect/sensor.py b/custom_components/audiconnect/sensor.py
index 5cda2921..6952368a 100644
--- a/custom_components/audiconnect/sensor.py
+++ b/custom_components/audiconnect/sensor.py
@@ -2,6 +2,7 @@
 
 import logging
 
+from homeassistant.components.sensor import DEVICE_CLASSES, SensorEntity
 from homeassistant.const import CONF_USERNAME
 
 from .audi_entity import AudiEntity
@@ -27,7 +28,7 @@ async def async_setup_entry(hass, config_entry, async_add_entities):
     async_add_entities(sensors, True)
 
 
-class AudiSensor(AudiEntity):
+class AudiSensor(AudiEntity, SensorEntity):
     """Representation of a Audi sensor."""
 
     @property
@@ -39,3 +40,13 @@ def state(self):
     def unit_of_measurement(self):
         """Return the unit of measurement."""
         return self._instrument.unit
+
+    @property
+    def device_class(self):
+        """Return the class of this sensor, from DEVICE_CLASSES."""
+        if (
+            self._instrument.device_class is not None
+            and self._instrument.device_class in DEVICE_CLASSES
+        ):
+            return self._instrument.device_class
+        return None