Add date device_class to Twente Milieu sensors (#56579)

homeassistant/components/twentemilieu/sensor.py

@@ -12,7 +12,13 @@ from twentemilieu import (
 
 from homeassistant.components.sensor import SensorEntity
 from homeassistant.config_entries import ConfigEntry
-from homeassistant.const import ATTR_IDENTIFIERS, ATTR_MANUFACTURER, ATTR_NAME, CONF_ID
+from homeassistant.const import (
+    ATTR_IDENTIFIERS,
+    ATTR_MANUFACTURER,
+    ATTR_NAME,
+    CONF_ID,
+    DEVICE_CLASS_DATE,
+)
 from homeassistant.core import HomeAssistant, callback
 from homeassistant.exceptions import PlatformNotReady
 from homeassistant.helpers.dispatcher import async_dispatcher_connect
@@ -74,6 +80,8 @@ async def async_setup_entry(
 class TwenteMilieuSensor(SensorEntity):
     """Defines a Twente Milieu sensor."""
 
+    _attr_device_class = DEVICE_CLASS_DATE
+
     def __init__(
         self,
         twentemilieu: TwenteMilieu,