Prevent how "last_changed" gets reset after reboot

[julesmartens]

Hi all,

Sometimes I forget to timely replace a battery in one of my battery-powered devices, - typical a PIR or door-window sensor. I noticed that the indicators for battery level are not much reliable.
As result I’m too late replacing batteries. The devices run out of power and communication to HA stops.

To improve this, I want to monitor state changes. If a state hasn’t changed for more than a week, I want HA to send a notification to check its battery.

I think I can determine this in YAML with this code to find the time since last state change.

{{ as_timestamp(now()) - as_timestamp(states.binary_sensor.bijkeuken_deur_sensor_106.last_changed) > (3600*24*7) }}

Next step would be an automation to trigger a notification if the above is true.

It works but only problem is that after I reboot HA, the last changed status gets updated.

In the image you see the status of sensor “irresponsive…” is true (last change more than 7days old), changes to false after a reboot. This while the state of the door sensor remains open, because the battery is depleted.

How can I prevent that “last_changed” gets updated after HA gets power cycled?

[123 (Taras)]

The answer to your question is: You cannot prevent it.

It’s a long-requested feature (value of last_changed survives a restart) but has never been implemented.

2019 Feature Request

Retain last state change data of a sensor after reboot

I would really like to see the last state change of an entity retained through a reboot. My use case: I have a binary sensor talking to a remote Hikvision camera’s PIR motion in my mother’s apartment. I know I can drill down into the state history, but it would really be nice to know that the at a glance “12 minutes ago” is an accurate indication of last motion detected, and not just the time since the last reboot. Thanks.

2020 WTH

What the heck is with the 'latest state change' not being kept after restart?

Every reboot I loose so much data about entities that I would like to keep on. Last time guest visited my house? Last time heating unit went on (to be checked in summer)? Last time never-used light changed? The answer is always the same: x hours/days ago, where x = date of restart. I know I can use automation and store that data in input_date or whatever… But it’s not easily visible in UI, i.e. as a secondary-info. [image] That light was on last time 3 months ago, not 18 hours.

2022 WTH

Persistent version of "last-changed" for the UI?

Something that has always annoyed me is how the “last-changed” attribute is handled after a restart. I understand why it’s changing as it’s technically unavailable but it’s not very helpful when you’re using it in the UI. On my security dashboard I only really care about the time a window state changed from on/off, not the fact that HA restarted and changed all my windows to 1 minute ago… What’s the likelihood of a new “last-changed” attribute that persists state between restarts so I don’t nee…

The workaround is to store the value in an entity whose value is able to survive a restart (like Input Helpers and Trigger-based Template Sensors).

[julesmartens]

thanks. I was not aware of that.
Any known workaround maybe?

[123 (Taras)]

Known workarounds are mentioned in my post above.