[Home Assistant] Restart Time

automations.yaml

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# Automations / Restart Time
# Publish timestamps to MQTT broker on start and shutdown.
################################################################

- id: restart_time_start
  alias: Publish Start Time
  description: Publish current timestamp to MQTT broker on startup.
  mode: single
  trigger:
    - platform: homeassistant
      event: start
  action:
    - service: mqtt.publish
      data:
        topic: homeassistant/start
        payload: "{{ now()|as_timestamp }}"
        retain: true

- id: restart_time_shutdown
  alias: Publish Shutdown Time
  description: Publish current timestamp to MQTT broker on shutdown.
  mode: single
  trigger:
    - platform: homeassistant
      event: shutdown
  action:
    - service: mqtt.publish
      data:
        topic: homeassistant/shutdown
        payload: "{{ now()|as_timestamp }}"
        retain: true

sensors.yaml

################################################################
# Sensor / Restart Time
################################################################

# Sensor for Home Assistant start timestamp.
- platform: mqtt
  name: Start Timestamp
  unique_id: 120a114d-a8a1-4364-8d43-a35954b19239
  icon: mdi:timer-outline
  state_topic: homeassistant/start

# Sensor for Home Assistant shutdown timestamp.
- platform: mqtt
  name: Shutdown Timestamp
  unique_id: affce05d-153b-48f2-af61-1333e50c2163
  icon: mdi:timer-outline
  state_topic: homeassistant/shutdown

# Sensor for Home Assistant difference between start and shutdown times.
- platform: template
  sensors:
    restart_time:
      friendly_name: Restart Time
      unique_id: c252bb03-374f-41a9-9e41-d1e1e02b9d90
      icon_template: mdi:timer-outline
      unit_of_measurement: s
      device_class: timestamp
      value_template: "{{ (states('sensor.start_timestamp')|float(0) - states('sensor.shutdown_timestamp')|float(0))|round(1) }}"