diff --git a/homeassistant/components/smarttub/binary_sensor.py b/homeassistant/components/smarttub/binary_sensor.py
index 04a6bb9b72a..bbeece36655 100644
--- a/homeassistant/components/smarttub/binary_sensor.py
+++ b/homeassistant/components/smarttub/binary_sensor.py
@@ -1,5 +1,4 @@
 """Platform for binary sensor integration."""
-from datetime import datetime, timedelta
 import logging
 
 from smarttub import SpaReminder
@@ -17,8 +16,6 @@ _LOGGER = logging.getLogger(__name__)
 
 # whether the reminder has been snoozed (bool)
 ATTR_REMINDER_SNOOZED = "snoozed"
-# the date at which the reminder will be activated
-ATTR_REMINDER_DATE = "date"
 
 
 async def async_setup_entry(hass, entry, async_add_entities):
@@ -83,12 +80,10 @@ class SmartTubReminder(SmartTubEntity, BinarySensorEntity):
         return self.reminder.remaining_days == 0
 
     @property
-    def device_state_attributes(self):
+    def extra_state_attributes(self):
         """Return the state attributes."""
-        when = datetime.now() + timedelta(days=self.reminder.remaining_days)
         return {
             ATTR_REMINDER_SNOOZED: self.reminder.snoozed,
-            ATTR_REMINDER_DATE: when.date().isoformat(),
         }
 
     @property
diff --git a/tests/components/smarttub/test_binary_sensor.py b/tests/components/smarttub/test_binary_sensor.py
index 8229372e904..5db97310c56 100644
--- a/tests/components/smarttub/test_binary_sensor.py
+++ b/tests/components/smarttub/test_binary_sensor.py
@@ -1,6 +1,4 @@
 """Test the SmartTub binary sensor platform."""
-from datetime import date, timedelta
-
 from homeassistant.components.binary_sensor import (
     DEVICE_CLASS_CONNECTIVITY,
     STATE_OFF,
@@ -25,7 +23,4 @@ async def test_reminders(spa, setup_entry, hass):
     state = hass.states.get(entity_id)
     assert state is not None
     assert state.state == STATE_OFF
-    assert date.fromisoformat(state.attributes["date"]) <= date.today() + timedelta(
-        days=2
-    )
     assert state.attributes["snoozed"] is False