How is the "history comment", on history graphs, generated?

Development
1

I’ve been monitoring the MQTT activity that reports an RSSI value from Tasmota running on an ESP8266 to make sure it’s working. The telemetry interval in Tasmota is set to the default of 5 minutes. Using the history graph for the RSSI sensor, I see this:

Motion%20RSSI

The sensor is defined as follows:

- platform: mqtt
  name: "Garage Motion RSSI"
  state_topic: "tele/motion01/STATE"
  unit_of_measurement: '%'
  value_template: "{{ value_json.Wifi.RSSI }}"
  retain: true
  icon: mdi:signal

Does the “6 hours ago” comment mean that the last update was 6 hours ago or does it mean that the last change in the history was noted six hours ago? In other words, if the value never changes, will the history comment just grow longer and longer even though new, identical values are reported?

2

In my experience the comment shows the time elapsed since the last state change. Regardless if the device is reporting a value or not.

The last update can be checked with the ‘last updated’ property however.

{{ states.sensor.garage_motion_rssi.last_updated }}

3

Do you know if there is a way to check this value from the web interface or do I have to do some programming?

4

Just type what @metbril showed in the Templates page.