Format time duration readably

[mariusz-schimke]

Describe the enhancement

I have several sensors that report duration—usually in seconds—such as this one from ESPHome tracking gas consumption time. The values can range from just a few seconds up to several hours. Other sensors I use span durations from seconds to days or even years. Let me give you an example entity with the device_class of duration:

Now let me change its unit to seconds for comparison:

When the unit is left as seconds, it becomes hard to interpret larger values—you’re forced to do mental math to understand them. On the other hand, if you switch the unit to hours, you lose the ability to see shorter durations accurately, like seconds, which might still be important.

What I’d expect instead:
I believe the UI should automatically format values based on their size. For example:

• < 60 seconds → display as x sec
• < 60 minutes → display as x min y sec
• < 24 hours → display as x h y min z sec
• ≥ 24 hours → display as x d y h z min

Why unit switching in the entity's settings is not a workaround (even though I mentioned it):
Changing the unit (e.g., from seconds to minutes) breaks compatibility with other parts of the system. For example:

• Template sensors and utility meters relying on the original unit of their source sensor don’t adjust automatically.
• The result is that their outputs become meaningless once the source unit is changed.

It would be great if Home Assistant could handle formatting duration values in a universal, human-readable way on the UI level, without requiring changes to the underlying unit or sensor logic.

Use cases

I have multiple duration sensors, including utility meters, whose values span from seconds to hundreds of days.

Visual examples

No response

Anything else?

No response

[make-all]

My expectation is that durations should be formatted the same way that timestamps are by default. By all means keep the manual configuration for use cases where having a fixed scale makes sense, but those use cases should also let the integration hint at the suitable UI unit of measurement, and the naming needs to be distinct from the unit_of_measurement of the underlying sensor, as the current reuse of naming is causing confusion.

[mariusz-schimke]

Yes, exactly, @make-all! There should be a clear distinction between the source unit of measurement, which is provided by the device and must remain fixed internally and unchangeable, and the unit or format that the user wants to display in the UI. Currently, when you change the displayed unit, it seems like you are only affecting the UI, but in fact, you break all linked entities and automations because they don't automatically adapt to the unit change. This causes inconsistency and unexpected behavior in the system.

And also, I agree with you there should be some default formatting of durations, like timestamps.

[mik-laj]

It looks related to: home-assistant/frontend#23338