Reading a iso8601 date from a mqtt date sensor

Configuration
1

Hi,

I’m sending both timestamp sensor entities and a date sensor entity to HASS via MQTT. The timestamp entity works fine but the date one fails as HASS indicates that a time zone is required. I may have a misunderstanding of what a sensor date device class is for … or ?

The error I see in the HASS log is:

Value error while updating state of sensor.net2hassmqtt_test_device_05_timestamp_date_only, topic: 'net2hassmqtt_test_app_1/net2hassmqtt_test_device_05/timestamp_date_only' with payload: b'{\r\n  "attributes": {},\r\n  "state": "2026-12-31"\r\n}': Invalid datetime: sensor.net2hassmqtt_test_device_05_timestamp_date_only provides state '2026-12-31 00:00:00', which is missing timezone information

Seems clear … it wants a timezone. Thing is I do not understand how a timezone would relate to a date. A timestamp sure (and very good), but a date? If I send it as midnight in one timezone and the HASS system is in another time zone it is “possible” that the displayed date would change. What is the purpose of the date device class?

I appreciate guidance. Thx.

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Is it that a date is always send as a timestamp with the time of day always 00:00:00 and with the sender’s time zone? This, I think, is what the error message is saying.

So while the time of day is technically not required the time zone allows the reader to known when that date starts and ends in their local time zone. Correct?

I need to run a few tests to understand how HASS displays it. My expectation is that it will always display as a date (without timezone) but the time zone is available.