add time_zone aware attribute 'last_seen'

[Mariusthvdb]

Is your feature request related to a problem? Please describe.

trying to replace as much custom components/integrations with core as possible, I am stuck here, using the Composite integration which allows me to use an attribute last_seen and calculate the timezone difference between home and the tracker:

      marijn_tz_offset:
        friendly_name: Marijn time zone offset
        unit_of_measurement: hr
        value_template: >
          {% set state = states.device_tracker.me %}
          {% if state.attributes is not none and
                state.attributes.time_zone is not none and
                state.attributes.time_zone != 'unknown' %}
            {% set n = now() %}
            {{(n.astimezone(state.attributes.last_seen.tzinfo).utcoffset() -
               n.utcoffset()).total_seconds()/3600}}
          {% else %}
            undetermined
          {% endif %}

Describe the solution you'd like

the above solution, but using an additional attribute to the current set of attributes for the device_tracker.

Additional context
https://community.home-assistant.io/t/how-to-get-to-or-template-last-seen-on-person-or-companion-app-sensors/242988

and

https://github.com/pnbruckner/ha-composite-tracker#time-zone-examples

further info:

though the sensor geocoded_location has the Time Zone attribute:

we cant use the utc_offset filter on it like in the offset template above like:

{{(n.astimezone(state_attr('sensor.calltheboss_geocoded_location','Time Zone')).utcoffset() -
               n.utcoffset()).total_seconds()/3600}}

because of the type error:

so an time_zone aware attribute last_seen would be very much appreciated.
thanks for considering

[zacwest]

Is there a particular reason that you can't use the device_tracker's last_updated/last_changed?

[Mariusthvdb]

well, I thought I had described that reason above?

In need of a timezone aware attribute, to be able to calculate the time difference between a traveling tracker and the home instance. Last_changed wouldn't be useful since the tracker wouldn't need to have changed at all, and yes I did look at last_updated, but that isn't timezone aware is it?

did have a go at this:

          {% set state = states.device_tracker.calltheboss %}
          {{(state.last_updated.astimezone().utcoffset() -
            now().utcoffset()).total_seconds()/3600}}

but I am not very confident it does what I seek it to do, and I can't test it because I am at Home ;-)

[zacwest]

I guess I'm not understanding what this would do to augment the device tracker. Are you looking for a new entity from the device for its current time zone?

[Mariusthvdb]

Are you looking for a new entity from the device for its current time zone?

Not a new entity per se, an attribute 'last_seen' for the existing device_tracker would do the job. I did have a look at the last_seen of the life360 integration but that too doesn't seem to be timezone aware
if you read here Phil words it better than I do:

the ability to determine the time zone in which a device is located (base on GPS coordinates), and then being able to report times (such as last_seen and at_loc_since) as time zone aware datetimes in that time zone.

[Mariusthvdb]

Hi Zac, revisiting my HA templates, I wonder if this would be something you could once more have a look at. Still in 'need' for a native 'core' HA way to be able to calculate the time difference between the home server local time, and a device_trackers local time.

To see how many hours earlier or later that specific tracker lives, compared to the home location.

Hope you can once more consider this being a useful addition to the core sensors of mobile_app.
thanks,
Marius

[Petro31]

Personally, I think this would be better as a separate integration that makes a timestamp sensor, tz location sensor, and possibly other information. It's input would be a gps sensor, device_tracker, or person.

[Mariusthvdb]

well, that would be very nice indeed. we could then even dynamically compare trackers to each other.
since the android app does provide a 'current timezone sensor', guess my hope was this could be done for iOS too