diff --git a/homeassistant/components/binary_sensor/envisalink.py b/homeassistant/components/binary_sensor/envisalink.py
index 0aadcc247ea..f358f814dc5 100644
--- a/homeassistant/components/binary_sensor/envisalink.py
+++ b/homeassistant/components/binary_sensor/envisalink.py
@@ -6,6 +6,7 @@ https://home-assistant.io/components/binary_sensor.envisalink/
 """
 import asyncio
 import logging
+import datetime
 
 from homeassistant.core import callback
 from homeassistant.helpers.dispatcher import async_dispatcher_connect
@@ -14,6 +15,7 @@ from homeassistant.components.envisalink import (
     DATA_EVL, ZONE_SCHEMA, CONF_ZONENAME, CONF_ZONETYPE, EnvisalinkDevice,
     SIGNAL_ZONE_UPDATE)
 from homeassistant.const import ATTR_LAST_TRIP_TIME
+from homeassistant.util import dt as dt_util
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -63,7 +65,25 @@ class EnvisalinkBinarySensor(EnvisalinkDevice, BinarySensorDevice):
     def device_state_attributes(self):
         """Return the state attributes."""
         attr = {}
-        attr[ATTR_LAST_TRIP_TIME] = self._info['last_fault']
+
+        # The Envisalink library returns a "last_fault" value that's the
+        # number of seconds since the last fault, up to a maximum of 327680
+        # seconds (65536 5-second ticks).
+        #
+        # We don't want the HA event log to fill up with a bunch of no-op
+        # "state changes" that are just that number ticking up once per poll
+        # interval, so we subtract it from the current second-accurate time
+        # unless it is already at the maximum value, in which case we set it
+        # to None since we can't determine the actual value.
+        seconds_ago = self._info['last_fault']
+        if seconds_ago < 65536 * 5:
+            now = dt_util.now().replace(microsecond=0)
+            delta = datetime.timedelta(seconds=seconds_ago)
+            last_trip_time = (now - delta).isoformat()
+        else:
+            last_trip_time = None
+
+        attr[ATTR_LAST_TRIP_TIME] = last_trip_time
         return attr
 
     @property